I'm only mean when people are being utterly vile or otherwise idiotic (and even then my meanness is usually pretty mild) and I don't suffer fools gladly. Otherwise I'm a reasonably non-despicable person and I do think it's horrid when people are just plain spiteful and horrible for their own amusement and gain. "It takes strength to be gentle and kind"- an oft-quoted statement, but completely true. As long as you don't let people walk all over you, life is generally a lot less hassle if you show decency and kindness to people. Everyone has slip-ups though, and I think that's probably healthy and necessary for balance- and the benefit of experience, of course.
People who get off on being mean do so because they are so miserable and nasty they have no hope of getting off sexually, they can't masturbate because their retarded brain was only able to invent one boring fantasy that doesn't work any more.