I think people who are mean were not born mean. I think they become mean as a result of their upbringing and environment. Just as abusers become abusive as a result of abuse they received themselves. Ultimately, meanness shows they are hurting and in pain inside themselves. Or, like said above, they are envious of that person and need to put them down and feel superior because ultimately, they feel inferior. I think it just points to the fact that the person is in pain, in one way or another.