Same reason why your sexuality is something you're born with and which CANNOT be changed, and to say otherwise makes you a bigot, but your gender is something that CANNOT be determined at birth and is liable to change on the fly whenever you feel like it and to say otherwise makes you a bigot.
Same reason why your sexuality is something you're born with and which CANNOT be changed, and to say otherwise makes you a bigot, but your gender is something that CANNOT be determined at birth and is liable to change on the fly whenever you feel like it and to say otherwise makes you a bigot.