One of the necessary steps to legitimize looting people of their wealth is methodically destroying their moral right to have that wealth. Tell people they didn't earn it, or they stole it, or they used nefarious methods to accumulate it. If you play this right, people will come to believe that no rich person could possibly have come by that kind of money honestly.

Once you establish that all wealthy people gained their wealth unfairly, it's easy to justify to the population your right to take it from them for a "higher cause." Of course, the one doing the looting paints himself as a hero of the people, and if the people are gullible enough, he can often successfully sell this idea. It helps a lot if he passes the looted wealth around.

If you look at the moral reality, it's somewhat different than the stereotype the wealth redistributors are selling.

The Forbes 400

If you drop the level down to your basic millionaire range, the numbers are even less stereotypical.