Dude. Do you know any medical, social, physical/physiological facts about boys and girls? Have you ever changed a diaper or toilet trained or worked as a camp counselor or coached children's sports? Are you seriously in need of arguments against this?

Here's one. My cats are both fixed, and have been since before either of them experienced any sort of "cat puberty" equivalent. I'm still aware that drinking milk is statistically more dangerous for the male(not sexless) cat, that it is more important for him to drink lots of water and get exercise(higher risk of weight gain/kidney stones). I'm aware that the female cat no longer wants to play-fight, and because she is smaller and less muscular, I occasionally need to separate the two. It would be less of an issue if they were both males.

Understand? These are just cats. The differences between male and female children and eunuch male and female adults(to say nothing of intact male and female adults) are vast and far better studied. Do your own research instead of demanding others do it for you.