It's just selfishness and narcissism. Any legislation designed to protect women can be applied to trans men easily enough when it's clearly about being female. Switch things around and remove the connection between "pregnancy" and "female", though, and it's inevitable that that will be used by the people who already discriminate against women every chance they get.
I'm pretty much at the "grow the fuck up, not everything is about pandering to your ego" stage with female TRAs. Nope, sorry, growing a scraggly little beard doesn't remove you from the category "female", which also means that policies designed to benefit women also benefit you, at least if you don't manage to sabotage them in moment of throwing toys out of the pram narcissistic rage.