No fighter who has made it to a degree you have heard of them is a psychopath. How a person goes about thier business in a ring/cage isnt a reflection of that person's complete personality. If it were, every single soldier who had ever been to war and shot someone, would be a psychopath (using the examples/requirements here). I honestly dont think a psycho could stick with the training, and some of the things required (training is give and take, not just take,take,take) to make technical progress.
Now if you want to talk about folks who hang around the sport, or even douches who pretend to have a background, that is another subject.