I think there's a problem because "evil" cannot be defined so everyone agrees to what it is. I don't think it is a very useful word; it's kind of like the word "nice" applied to someone. Behavior is behavior and is committed by humans. We have no way of knowing if we would behave a particular way under some other circumstances or not. Some people seem to enjoy, or not regret, doing horrible things to other people and society can't have that. But I don't think criminal, mentally ill, evil, any of those terms are very useful in helping work on either society's or an individual's problems.