If your getting issues with violent AMOG's in the Club/Bar your going to, it's not your issue to handle, it's the Venues issue. However, from experience I know that most will usher out the trouble makers, and will be banned from the Club if they continue to stir up trouble.
True Story: I've seen some scary stuff while working as a Bartender in Tokyo, when a black dude who was on crack, got out of control and tried to kill the bouncer and almost stabbed him with a kitchen knife.
He's now in prison, after being caught.
My advice is, don't Club to venues that can't or aren't dealing with these type of problems. But if it does happen to occur, learn Jujitsu which is full-contact martial arts, alot of good moves are easy to learn and simple. Un-like others that are more sport like and take along time to really master.
You can also use it as a DHV.
I've used it as one of my casual DHV's, and it worked really well.
