Why do people always need to pick on the weak?

Like homosexuals, the elderly, the poor, children, and animals. Especially when there are tons of powerful people who truly deserve to get picked on, like Politicians, corporate CEO's, teachers, Street Preachers, Lobbyists, child abusers, dictators, schoolboard intendents, authoritarian teachers. Or are they really more abused, and if theyre abused, humanity becomes more blessed.