Gender identity is an unfalsifiable claim. It is an unprovable belief. Someone claims to be a gender and we are just supposed to take their word for it, no proof necessary.
But what if it became provable? What if a machine were invented that could actually show someone's gender identity? Proof, real, actual proof. No more blind faith required.
Except, then the invention is destroyed and the inventor's assistant murdered.
Who would do that? Who would kill to keep gender identity unprovable?