Street-Fighting Women

It looked for all the world like one of those fat-suit wrestling competitions. Two rather large Puerto Rican women in a roly-poly catfight on a sidewalk on Broadway in the 30s. Nothing attracts a crowd like a crowd, but maybe 10 bored people looked on when me and a friend passed by. Even the cops treated it like a joke.
I never quite know what to do in those situations, and I hate gawkers looking on for cheap entertainment, yet of course have to fight my remaining journalistic instincts to witness violence.
In DC once some moronic kid in Mt. Pleasant was firing a gun northward at the end of the street. Instead of ducking back in to my bar, I started following the kid. A restaurant owner in his entryway looked at me like a was a lunatic and said "are you crazy?" and told me to stand back.
As PJ O'Rourke once said, violence is interesting. Unfortunately, he's right. The question is what is the moral thing to do in such situations? Do you have a moral obligation to do something?
It is like the case of people rescuing drowning swimmers even though it places them in harm's way. I think way back to the jet that hit the 14th Street bridge in DC in the early 80s. As you might remember, a man on the banks of the Potomac jumped out and saved a passenger in freezing, ice-choked water.
Then there's the guy who rescued someone on the subway tracks in NY by leaping onto the tracks and pinning both under the undercarriage of the cars.
They say that people do these kind of things because they want others to react the same way if they were in trouble. The question comes down to more than guts. As the subway savior said, he just didn't think about it, he just did it.