Who's talking about nut jobs?
Have you ever gotten mad enough or annoyed enough at someone that you took a swing at them, only to immediately regret it afterward, because you just saw red for a minute and shouldn't have lost control like that?
Now imagine that happening to a mutant with powers like Rouge or Wither (we can't use the characters themselves, because they have no control over their powers) or just some generic strength power; they've got control over their powers most of the time, and are perfectly nice, well-adjusted people. But if they ever get mad or annoyed enough, and lose control for just that instant, the other guy could wind up seriously hurt or even dead.