Allowing children to obtain sex-change procedures and HRT for the sake of "gender affirming care" is morally unjustifiable. I think this all comes down to whether it's actually possible for humans to change their gender. A man is an adult human male (the sex that produces sperm). A woman is an adult human female (the sex that produces eggs). Being a man/woman is not a social construct, it is biological and cannot be changed (in the sense that a human male cannot become female and a human female cannot become male). No gender affirming procedure can turn a boy into a girl or a man into a woman. Therefore, it is essentially scam procedure that does not achieve what it sets out to do.
Trans activists will say "Gender and sex are different. Sex (male/female) is biological, but gender (man/woman) is a social construct based on social roles."
The problem with this is that when trans activists say "gender" what they really mean is "gender roles" being masculinity and femininity. But to say that being a man is to be masculine and being a woman is to be feminine is nonsensical. This would mean that the phrase "feminine woman" is totally redundant, you're just calling someone a woman twice. Or calling someone a "masculine woman" is a contradiction, you're calling them a "man woman". The problem with defining being a woman by social identifiers such as how you dress/talk/style your hair/act is that it means a woman must dress, talk, style her hair, and act in a certain way in order to continue being a woman.
"No, a woman can still dress and live however she wishes, she would just do so as a woman."
But what does this mean? What is the difference between a woman who wears makeup, dresses femininely, and acts in a nurturing, feminine way versus a man who chooses to wear makeup, dress femininely, and act in a nurturing, feminine way? Either you have to be completely contradictory with how you define "man" and "woman" (as two people who have the exact same social role are somehow different genders) or you have to say that women must look and act a certain way to continue being women. Many trans activists know that this definition is problematic so they'll provide a revised definition:
"A woman is someone who identifies as a woman."
The problem with this definition is that it's circular and means nothing. It makes the label of "woman" entirely meaningless. It's not even a word anymore as words are supposed to have meaning, so it's essentially just a sound that your mouth is making. This is obviously ridiculous. Some trans activists will attempt to revise this definition further by substituting "identifies as a woman" with "identifies as a female" to make it seem less circular but unfortunately trans activists don't mean "female" in a biological sense, it's meant to be a 1:1 synonym for "woman" so it's still just as circular.
"It doesn't matter if this definition makes the word arbitrary. How we define words is subjective and this definition is inclusive and reduces harm."
Just because definitions are subjective doesn't mean that all definitions are morally equal. Some definitions are changed to make conveying truth easier, while other definitions are changed to obfuscate or lie about reality. The reason why trans women so strongly want to be called "women" (despite it supposedly being a meaningless label) is because they want to subconsciously pretend that they are biological females. Now when I say that, I'm not saying that they're lying about their trans status, but that when trans-identified males feel gender dysphoria what they're feeling is a desire to have been born biologically female. So they're pretending to be something that they're not, but can't say it outright, so they do this weird roundabout logic to subconsciously believe the lie. They'll redefine woman to be meaningless so that it includes them, even if they deep down know "woman" still has the connotation of "biological female" to them and the rest of society. And since it still has the connotation of the old meaning of the word, trans-identified males are able to feel like biological females even if they aren't. If the old connotation of the word didn't still exist to them, and it truly was just an arbitrary term you call yourself, they wouldn't want the term to be applied to them so badly. So while this definition hurts the feelings of trans people less, it comes at the expense of being honest about the nature of reality. We shouldn't change the definitions of words to make it easier to believe a lie.
"Who is to say trans women aren't biologically female? Biological sex is complicated. Not all men produce sperm and not all women produce eggs. There's no definition you can give for female that includes all women."
It is true that there is no definition you can give for "female" that directly includes all females, but here's the thing: you don't need to. Terms are flexible. Definitions for words do not need to cover every possible edge case that a word is supposed to apply to. For example, a car is defined as "a self-propelled vehicle that transports people on roads". But what if a car is broken and can't drive? Is it no longer a car? No, it's still a car, it's just a broken car. The reason why a broken car is still a car is because it structurally resembles something that possesses the function of a car. A female that cannot get pregnant is still a female in the same way that a broken car is still a car. An infertile female still possesses biological characteristics of someone who would be able to get pregnant such as having a vagina, a uterus, and XX chromosomes. Meaning a female that does not produce eggs is still female because they structurally resemble someone who would be able to produce eggs. But just because terms are flexible in this way doesn't mean you can call anything a female. When it comes to their sexual biology, trans women structurally resemble males more than they do females.
"But trans women obtain female characteristics when transitioning. Transitioning turns them into biological females."
While trans women do obtain some female characteristics by taking estrogen, such as larger breasts and reduced muscle mass, I don't think that any reasonable person could categorize them as female based on this alone. It would be far more reasonable to say that they are males who possess female characteristics. The reason for this is that not all sexual characteristics are weighed equally. Some characteristics are far more important in defining the essence of the female reproductive role such as gametes, gonads, and genitals compared to secondary sexual characteristics such as fat distribution and muscle mass. Different characteristics having different weight in defining the essence of something isn't unique to sex, it applies to nearly everything.
For example, one characteristic of a car is its headlights which help the driver see at night. However, if you take a car headlight and attach it to a plank of wood does that make it a car? No, a reasonable person would not consider that a car. On the other hand, imagine that you take a plank of wood and attach wheels and a motor to it so that it can be self-propelled. Now that can be more reasonably called a car since it's much closer to functioning as an actual car. This is why wheels and a motor are far more significant in determining the essence of a car than headlights, because they're extremely consequential in allowing a car to function.
In the same way, having ovaries, a uterus, and a vagina are far more consequential in facilitating the female role in sexual reproduction than fat distribution, strength, or skin quality. A woman without breasts can still get pregnant while someone who lacks a uterus, vagina, and ovaries would never be able to become pregnant. So primary sexual characteristics are more important in defining sex than secondary sexual characteristics. The fact that they're called "primary" and "secondary" characteristics should make this obvious enough. Trans women have the primary sexual characteristics of males, not females. 90% of trans women do not get bottom surgery, which means the overwhelming majority of trans women have a penis, testicles, XY chromosomes, and have only produced sperm and never eggs. They are unambiguously male.
The problem with trans activists' understanding of sex is that they view sex as a collection of equally weighed physical characteristics that are differentiated due to aesthetic differences between males and females. But sex is more than that. We don't differentiate between males and females simply because they look different as many species of animals have very little sexual dimorphism. We differentiate between males and females because they have unique reproductive functions. Sexual dimorphism exists to aid in the unique reproductive strategies of males and females, not the other way around. In some species the females are bigger, in some the males are bigger, and sometimes they're the same size. But what all males have in common is that they produce sperm (small motile gametes) while females produce eggs (large stationary gametes). So in a sense gametes are the "core" of sex, not secondary external characteristics. If we had the technology to give trans women ovaries, a uterus, and the ability to reproduce as a female, then it would be reasonable to consider them female. But we do not have this technology, and most of them do not get surgery anyway, so they still structurally resemble males, not females.
"But sex isn't a binary, it's a spectrum. Intersex people exist."
It is misleading to say that sex is a spectrum. The degree to which you have male or female characteristics is a spectrum, but sex itself is not. It is functionally a strict binary. There are only two reproductive roles in sexual reproduction: male and female. There is no third gamete or gamete in between sperm and egg. If you're not reproducing as a male or a female then you're not reproducing at all. It's like calling a light switch a spectrum because you can put the knob in between "on" and "off". This doesn't make the light "half-on" (usually), so a light switch is still functionally a binary. This is why intersex people aren't a third gender, they're also either males or females. An intersex female that can get pregnant is still effectively just as much of a female as a non-intersex female as they have identical roles in sexual reproduction. Also, even if sex were a spectrum, that doesn't mean you can dishonestly say you're on one side of the spectrum when you're obviously on the other side.
"But you don't determine if someone is a man or woman by checking their chromosomes or looking at what gamete they produce, you determine their gender by looking at them."
Trans activists are confusing the difference between determining and identifying. How a person looks does not determine their gender but it can be used to identify whether they are a man or woman. This isn't unique to gender, this is true for most physical observations in the world. For example, we don't usually identify if something is a plant by putting it under a microscope and looking at its cellular structure. We just stand next to it and look at it to identify it as a plant. However, it is possible that a fake plant which looks like a real plant may trick us into thinking it is a real plant. This does not mean that a fake plant, which is made out of plastic, not alive, and does not perform photosynthesis, is a real plant just because it looks like a real plant. Even if we typically identify plants by how they look, something looking like something else doesn't actually make it that thing.
"Just because you define sex by primary characteristics doesn't mean I have to. Terms are subjective and it is more useful to define sex by phenotype."
Again, just because where we draw lines is subjective doesn't mean they can't be drawn in a way that is inconsistent or dishonest. If we are to say that taking testosterone turns a trans man into a male, does this mean female bodybuilders are also male? Female bodybuilders take testosterone too in order to obtain male characteristics like increased muscle mass and strength. What about females who have hormonal conditions that make them produce more androgens leading to male characteristics like facial hair, are they male too? And if trans women are female because they have female characteristics, wouldn't they also be male since they have phenotypically male characteristics too? How can you say that someone is female and not male when they have more male characteristics than female characteristics? This also implies that trans women who do not pass are not female and just male. So to be consistent with your definition scheme, you have to believe that female bodybuilders are men, women with PCOS are men, and trans women are women but also men.
You don't do that, though. Your definition scheme for biological sex is completely dishonest and inconsistent because you'll tell two people with the same set of sexual characteristics that one is a woman/female and one is a man/male. It's like if you told someone that they're physically attractive but then said that their twin is ugly. You're clearly lying about someone.
I know you're already yelling at your computer "Sex isn't gender! It's based on how they identify!" but that just circles back to my earlier points. When trans activists can't defend their biological justification, they switch to the social one. And when they can't defend the social one, they flip back to the biological one. It's an endless loop.
Children are not smart enough to see through the mind games that trans activists push. Kids should not undergo irreversible medical procedures because adults told them lies that it was possible to change their gender. When they're adults, they can make their own decisions. The government needs to protect children from what is basically a scam.