I talked about anarchism with someone recently, and "evil people" was their main argument.
I've been thinking about it a lot. My point of view is that power structures give those evil people an unmatched oportunity to gain power over others. I think most of them are in politics, be it in democracy or authoritarian regimes. They are the best at climbing hierarchies and have the motivation to do so, unlike most people.
But still, it seems that having evil people in politics is somehow better than having to deal with them directly for a lot of people. It may be the fear of unknown - governments might do bad things on a much bigger scale, but at least they are predictable. That's just my interpretation though.