That's a reasonable point. I was introduced to the idea that "gender is a social construct" well before I was introduced to the idea of transsexuals, so I had some opportunity to think about that as a separate issue from the idea of "Some people want sex change operations."

I was one of the top ranked students of my graduating high school class and I tend to speak my mind and do other things that tend to be socially acceptable for men, but not women. Women like me tend to get a lot of flak from the world for failing to "know their place" and they get a lot of flak in a way that questions their gender identity and that causes them to wonder about gender roles and their own identity and so forth.

So when I was younger, I wondered things like If having an opinion and speaking my mind is "masculine," does that say something about my sexuality?

So I found the whole concept of being a transsexual pretty confusing when I first ran into it. I wondered did that apply to me in some way and where do you draw certain lines.

I ran into someone online who talked about having "beard envy" and that was an Aha! moment for me. I have never felt that way and that was an incident that helped me feel clear in my mind about the ways in which "gender is a social construct" negatively impacts my life as a woman and really has nothing to do with things like sexuality or sex.

So I feel clear that, yup, "I'm a woman" and that's sometimes problematic and uncomfortable because of how the rest of the world would like to dictate to me what that means about how I should dress and how I should behave and so forth. And that fact is even more problematic for some people than it is for me because they are intersex or they feel their body is the wrong sex (etc).

So I fully get that it's a weird idea the first time you run into it and it can take some time to understand the distinction people are trying to make.

If you want to say "I have a PhD in biology, so I feel entitled to insist my (offensive) opinions about sex are right!" then I think you have some obligation to try to understand the distinction people are trying to make. He doesn't appear to be doing that.

If you are just a software engineer trying to figure out how to code up radio buttons on a website and not someone actively promoting your ideas about biological sex, eh, you may have no real need, personally, to spend a whole lot of time trying to parse these things. At that point, it makes sense to basically go "Well, not really something I'm interested in and since I don't have an informed opinion, I will largely leave it to other people to argue about this."

If you don't know much about math, you probably aren't going to tell people with PhDs in math that they are wrong because you don't understand what they are talking about. That same general standard should apply in this case as well. It's okay to not know everything about every subject, assuming you don't try to cram your uninformed opinions down everyone else's throats.

I will add that human categories are just that: human made concepts. Animals like the platypus didn't consult with human categories before they evolved into mammals that lay eggs, which humans have an issue with because it flies in the face of our nice, neat categories.

Nature is full of examples of things that fail to be readily categorized by humans in a way that is convenient for us. Our desire to categories things often runs into friction with actual reality.

At that point, you have to admit that the mental is defective rather than trying to insist reality is behaving badly and should stop doing that already.