Because he's a magical girl! :tongue: I've always been wondering this too, I guess there isn't really a logical explaination to it, exept for like, some sorta foreshadowning that he's gonna have longer hair, like original Dante. Or maybe you could say, that since he released so much power, it made, uh, whaddaya call it? Idk, it just made his body do stuff quicker, so his hair grew, or something *shrugs*
1) There is general consensus of what is morally ok and what not for a lot of things, for example pretty much everyone agrees that it is not ok to kill somebody, whereas demons don't really seem to think so.
2) I don't think you can compare them to those kinda people :/ Also, to stay in the game's world, look at Dante. He also grew up in ghettos, and he ain't quite like the demons.
Personally, I don't think we're even supposed to view them just like humans that grew up under bad circumstances, otherwise it wouldn't portrayed as being ok to just kill them, if they'd be just like human beings.