The penis is a feature of a biological male. However, not everyone who is biologically male presents themselves as masculine, or even as a man, and some more closely match a feminine archetype in behavior and appearance.

Ah yes the good old argument: "YOU are responsible for complicating MY simple world by raising questions I am uncomfortable with. OBVIOUSLY penis=boy, vagina=girl, and there are no sociological or political things to think about there, and if you cant explain it in a way that is just as simple as I see it, then you must just be confused or lying" I love all the variations of this one, because there is no lower limit to how simply you can describe inaccurate or incomplete information. Accurate information, on the other hand, just IS complex a lot of the time, and often can't be described simply. And when the comfort of a simple but incomplete idea is challenged, it is easy to deflect and give snappy responses that reject deeper thought. Then, when people get impatient with you, you can just move on to how wrong and debased it is for people to be so rude towards someone with an opposing view.