It's just that in the end, saying someone is "stupid, retarded, idiot, dumbass, etc." is only some shortcut to expressing your disagreement with some acts that could be easily explained. These acts also have a better reason to be done than because the person is "stupid, retard, idiot, dumbass, etc." and that's the main problem of calling people that way; because you slowly learn to become blind about what's hapenning.
I wanted to add a little thing regarding Psychadelicon...
There's something to consider when someone is calling another "faggot" or such; the expression itself has lost most of his sense recently (I wonder why - but I think I know - ...homosexuals aren't necesserily stupid) and only means "retarded" or "idiot". So, of course there's no elements of proof that the kid is homosexual but that wasn't the point of the insult; it was only to tell that he was stupid (which again doesn't mean anything as explained before).