It's literally being done. Dudes are pretending to be women & are being allowed in women's locker rooms despite being physically stronger & larger & literally still having dicks. And left wingers are celebrating them for it. Are you denying that this is happening?
Where is your capacity for adversarial thinking? Not just that, but a person believing they are trapped in the wrong body & hating their own genitalia is basically a prime indication of serious sexual abuse & mental illness. And those are exactly the sort of people who most often abuse others.
You aren't free to lie about reality, to force others to participate in the lie, & to cross lines drawn based on immutable biological differences.
If you deny something as basic as the binary reality of biological sex then all of your principles are meaningless. If you can't define what a man or woman is then it's like saying 2+2=5, we don't live in the same world & we don't play by the same rules. You are allowing the underlying reality on which basic individual rights are built to be destroyed. You can't protect women & children if you let "women & children" be defined by feelings & the irrational whims of mentally disturbed people.