I don't think that everyone is really capable of violence.
Technically they're physically able, but without a mental command to act, they are not capable.
There are different kinds of violence. Each needs to be studied and understood. One needs to able to recognize them.
I am a very non-violent, non-confrontational type of person. I'd like to think that I'm all macho and able to turn on a switch and be ruthless, but I'm not quite like that. I hope that training and mindset conditioning will allow me to act appropriately if the need arises.
"If you're not shootin', you should be loadin'. If you're not loadin', you should be movin', if you're not movin', someone's gonna cut your head off and put it on a stick." -Clint Smith