No I don't believe its a joke. :/
People do not seem to understand that acceptance of a gender variance is not contingent on sexuality preference. I find myself constantly fighting the misconceptions of bisexual women on this forum. What I like about men are their manly qualities and what I like about women are their womanly qualities. A GM does not fill out the expectations of what a woman that I would find sexy, would look like in my mind, even wearing the "right clothes.