And for the times I've used violence, even in a reflexive, no-time-to-think situation, I've regretted raising my hand to another. Regretted it to the point of nausea, insomnia and worse. Even thinking about situations from years ago, as I'm doing now, I feel miserable. Yeah, in a way, weakness is easier as you said, "an excuse for not acting," but the strength not to fight when you have the strength to fight requires a courage and a discipline that have to be practiced and reinforced every day.
No, your husband failed Friday night, just like I failed in those past situations. There are a skabillion rationalizations, and in this society, everybody will tell you that it's okay, the situation might have worked out far worse, and it was a measured and judicious application of violence. But if your husband is anything like me, it doesn't feel that way. And if he's tuned into you at all, he gets your emotional state as well.
Our society is awash in violence, and we are inundated with the message that might makes right. After all the trouble our culture has gone to instilling those feelings and emotions, it would be nearly miraculous if you didn't want to see some rough "justice" meted out to those bullies who harassed your friend. We like to pretend that advertising (for example) doesn't affect us, our emotions or our choices, but it does. The folks who run those big corporations wouldn't be plunking down so much money to ad agencies if it didn't work. Violence has not only ad agencies, but popular entertainments (from movies to TV shows to video games to books to--well, you get the idea) and real world enactments buttressing its message on a near constant basis.
Talk it out, hug it out, process and re-process, build your relationships, expand your circles, create and maintain your own peace and encourage it in those around you. It's the way we overcome the proprietors of violence.