I've noticed a couple of different reasons for this. 1: When you train a level of aggression into people and create a reward response in their brain for committing violence then it's very possible it can easily become their go to solution for most problems. 2: People already prone to aggression and violence are the people most likely to be attracted to it. Both of these groups though tend to be more the MMA bros that I've been in contact with. I've not noticed as much with other groups of martial artists.