But the reason we are now allowed to identity as we wish is because we now know that gender and sex emerge from our experiences rather than biological fact. So what we traditionally known to mean being homosexual or heterosexual (when you fancy people of the opposite gender/sex) no longer applies.
Of course they still apply. What you have in your pants and what you want to have there remains different and distinct from where you want to stick it.
For them, those traditional notions may not apply but for the rest of us they do. I am a bloke who fancies women and I identify as such. Whats wrong with that?