I don't know all martial artists. I've done martial arts, and I am mostly a pacifist, etc. But I have heard stories about black belts who like to go out on the weekend and pick fights with people just for the fun of it.
These are the guys who are not martial artists, especially not true black belts.
Martial artists understand that they train for a purpose
other than hurting people, there is a discipline and honor in it. A real "black belt" should be the person doing everything possible
not to fight because they are the people that can truly cause pain. They are responsible enough to know that they can kill someone, but choose to turn the other cheek unless there is really no other option.
People who "do karate", etc and go out looking for fights are idiots with too much rage (and yes are fucked-up) but do not take the actions of a couple of assholes for those of a real martial artist. This is why I believe all these people going to train in "MMA" is dangerous, there is no message behind it, no philosophy, no moral or ethical teaching.
Rant over