Ah ok, sorry, couldn't understand the way it was phrased when I read it lol
If the kid has a penis and "shows it off" then that's up to him. If it's in public the I would discourage that anyway, whatever the child. And if it's when the parents aren't there, ie to other kids in school or something, then that's just something that's naturally gonna happen.
I think people are seeing all this as the parents trying to force something onto their child, whereas the parents are seeing it as trying to stop other influences being forced onto the child. I don't think it's really an issue if the kid does "show off" his penis (if they have one)