My brother went looking for a friend last night at a movie marathon, and he found him getting beaten into by 20 or so guys, he went in to help got hit and eventually police and security came in, after that his friend's carer didn't turn up so he had to walk several k's to his friends house with him.
My question is, if your friend is in trouble against what odds is it "ok" to leave your friend, personally i think you should back them up at any cost.