For those saying they would intervene... here's the problem:
In the situation presented by the OP, I don't know enough to interject myself into the situation. My best option is to simply be a good witness. Someone less risk averse may feel it's worth the risk to save the life of a stranger.
I think it's wrong to belittle those of us unwilling to risk our life, liberty, and happiness. The reality is that we aren't superheroes, and we have no moral or legal obligation to act like one.
I'm not sure if I saw a post that was belittling any of the responses to not to intervene.But maybe I missed it. I certainly wasn't trying to belittle anyone. So, I apologize if I came across this way.
The decision of whether or not to intervene is a very personal one. I'm just saying that this is what I think I would do (given the advantage of not having to make a split-second decision).
I have not been in a bar room brawl, but I have fought competitively in judo and know that someone being body-slammed could very easily sustain life-threatening injuries if not experienced in giving and receiving such throws. The scenario was body-slammed (presumably, onto concrete), unconsciousness, a couple of more blows while unconscious, and moving an unconscious person with unknown injuries, which itself could exacerbate an injury to become a life-altering injury.
At what point do I say enough...regardless of who was "right" and who was "wrong"? I say, for me, it's the point of unconsciousness. Boxing matches, judo matches, other martial arts matches do not allow the contest to go beyond this point. Why?
This is the point at which thefightis so one-sided that, for me, to stand by and do nothing would be a violation of my conscience.