I would intervene in some kind of way.. it depends on the situation.. I am not gonna standby and watch anybody get manhandled especially if its somebody that can't fend for themselves like an elder, girl or child..
To be honest, I'd probably be more reluctant / hesitant if its some guy is in trouble but I would more than likely end up doing something to help em' (You always think too yourself, if that was you, you'd want somebody to help you.) :2 cents:
I would call the police, but lets be honest 99% of the time police investigate situations after the fact of a crime has been committed, they are seldom there to save a person in there most desperate time and need of help.
That said, I don't embrace altercations or go out of my way looking for trouble, (like bloodshot mentioned, I mostly mind my own business) but the fact is, most of the time I am strapped up, and if I thought I could, would or knew I'd probably be saving somebodies life, I prolly would (I surely don't have or carry my weapon to go out my way too play a hero, I ONLY have it for personal protection) but sometimes you just gotta do what you got to do, when the time comes. :anonymous