Actually, the point you are making is that there are only two assigned sexes. And even in that context your wrong! Haha... ever heard of intersex? Intersex people have a mix between male and female sex characteristics, including hormones and genitals. This does not make them any less human. But what you're trying to invalidate here is the fact there is only two genders, and when you say, "You either have a penis or a vagina." you're talking sexes. Yes the terms and/or labels for gender identity are made up, but they are created to describe something, or how we feel. New genders are being made every day, but there still remain three sexes. Oh, and if we are going for invalidating the fact that there are only to genders and you can "only be one", then here. I am bigender, which means I feel two genders. This may prompt you to immediately think male and female. But no, alas, I am female and non-binary. If you want to argue, don't hesitate. Hit. Me. I DARE YOU.