Gender is characteristics that a society or culture delineates as masculine or feminine. So while you can't change your biological sex, you can change gender. Which is what trans people do.
But can't you see, that if gender is nothing but what society dictates and nothing more, then there is nothing to change. You are talking about changing a social construct, not the person. So it is immaterial, and he is still male with a bunch of ever shifting social constructs swarming through his mind. Understand?
