What do you think is wrong with that sort of statement?

It's a logical fallacy, relying on the arguer to convincingly refute the concept of the longstanding agreement on the meaning of language. Even though the world has agreed on the meaning of a man as chiefly being the contributor of sperm to create a child and of a woman being the contributor of the egg and the incubator of a child, Critical Theory types twist logic and language in their attempts at a challenge. They rely on weasel arguments of extreme edge cases (intersex people) and bad faith sophistry of their own made-up meanings applied to words whose common meaning have been gospel for aeons.

In reality, sure - you can call a person whatever you want to call them. You can make up your own new meanings for anything. That doesn't make it true to anyone else, given that the common meaning is backed up by all of the people in the world using it essentially forever. There's a reason why, as we grow up, the nonsense words that we made up as toddlers get left at the wayside.

To illustrate, let's try this little experiment; the next time you're facing an emergency - maybe there's a person who broke into your house with a gun - make sure you dial 472, and only 472. I say that 472 is the only number that will bring the police to your assistance. If it doesn't work, keep dialling 472 until the police eventually respond. I assure you that this is true and that you will not have to worry about the armed and dangerous home invader as soon as he hears those sirens. Godspeed!