There are two sexes. Gender only refers to words, not people. Don’t use their terminology.
Indeed, the terminology is designed to make rational discussion impossible. However, we’ve long since lost the gender = grammar battle. Gender now refers to a social-psychological construct. As a product of the imagination, the number of genders is only limited by the imagination. OTOH, with rare exceptions, there are only two biological sexes. We must not allow that distinction to disappear.