Back in the old country, I came across a guy beating the hell out of a woman. I pulled him off and gave him a pretty thorough demonstration of what being beaten felt like.
When I had him suitably "subdued" I called an ambulance (for the woman) and the police for the guy.
Got a nice thank you from the police and the woman (his ex).
A good grounding in martial arts is probably as good as a weapon in CQC.
About 10 years later I tried to stop another guy from beating his girlfriend and came close to getting a bottle in the face from the girlfriend and had to subdue them both - no good deed remains unpunished I guess