Stranger or not, its irrelevant, maybe you could save his life if you would step in, instead you did nothing.
I think you should have some alone time, think of your values, and why you are on this earth. Because like i said your a very low character, and you don't want to live your life like that.
I personally would love to be in a situation like this, i would have helped the person, and regardless of the outcome, i would be kind of self-realized, i would know that i didn't live my life for nothing.
Lol u need some alone time. My values are fine. You can be a captain kirk save a hoe if u want im not dieing for anyone. If i feel the risk is low i will do somthing but yea if i see 4 or 5 brutaly beating someone for trying to help i would be a fool to try to do the same . Im perfectly fine with it and have no problem sleeping at night