To be sure, many mean people enjoy being mean.
That doesn't stop them from disliking dealing with the kind of people who are willing to be friends with them despite their being the kind of people they are. That doesn't make them feel better when they get in a fight at home.
While it doesn't always work out very fairly in the end, it does frequently enough that it is rather stupid in the end to be a mean person.
Cheers,
Ben