You are the one who is missing the point regarding the relationship between gender and biological sex, that being that gender is a communication of biological sex. An accurate communication of this is vital for social stability, considering humanity’s nature as sexual beings. As has been the case throughout human history, the family is a fundamental building block of society, and sexuality plays a role in a family’s establishment. It should stand to reason then that sexually aberrant behavior such as transgenderism is a destabilizing factor for the whole of society