Whenever I have gotten into a discussion with people who support this stuff, it always ends up that they have fallen for the appeal to authority logical fallacy.
It has been declared this is what gender is by the authority and they put no thought into it.
You discuss it, and you can make them confused pointing out the flaw because biological reality exists and they know it. However, you're not the authority for what is correct. I have told this story many times on here but I had a big blow up with a long time friend about this and simply going, "ok, so trans women are women but you're wife and a trans women are still different, how would you define that difference?" He was completely stumped. "I hadn't thought about that." The dude's a fucking corporate lawyer.
He just accepted the trans stuff. I also know a lecturer at a college who has told me that students, mainly male are just told by her to shut up, stop asking questions and go along with it to do their gender studies adjacent course work because they literally can't answer the basic questions.
I know plenty of people who accept all this, "If that's what someone feels like, just go along with it." As if it's that simple. You mention any of the issues and it's the 1984 wrong think and everyone wants to shut it down, in a manner that it is like protecting me from saying the wrong thing.
It's all so fucking insane.