Their argument is that “gender is just a social construct”, without acknowledging that some of the most paramount aspects of human existence are “social constructs” (i.e language) and that gender is one of them. And without addressing why sexual taboos (like public nudity) are gendered - to them its a form of irrational injustice. But expore the social ramifications -through real and hypothetical examples- and you quickly find that it is indeed rational to treat bodies different according to their gender, and that human social psychology does have strong roots in human phsyiognamy.