[Zagill]

Gender as a concept distinct from sex is a way of describing an existing social phenomenon. Gender, though traditionally tied to biological sex, changes over time. What we define as "masculine" and "feminine" traits change as society changes, and can even differ between societies, despite the fact that male and female chromosomes have not changed. Just because no one had described this distinction before the last century doesn't mean it isn't legitimate.

[umanwizard]

The terminology of the debate gets confused a bit because while indeed the expectations of people’s behavior, dress, etc. based on their sex is indeed a social construct and has been probably since the beginning of humanity, that wasn’t what “gender” meant until very recently. As far as I can tell, “gender” and “sex” were completely synonymous until 50 years ago, even in niche academic communities, and until maybe 10 years ago among the general public.

[Zagill]

I will agree that the terminology could probably be better. But my original point is that this is a pretty high-profile issue and has been for a while, so anyone taking a hardline stance of "I'm gonna deny trans people until someone makes a good argument why gender and sex are different" is willfully ignorant at best.