Why does witnessing all this bother me so much?

I used to be the only girl to hang out with about 6 guys, 5 of them were my b/f of 7years friends - their g/fs came and went so they never really counted as they were sleazy guys. Anyway , the real question is some of the stuff they did to this one kid like haunts me i feel like i could have stopped it or spoken up for him. he was much smaller than them and lived 3 houses down from house we spent a lot of time at. it looked like a crack house - but somehow noone did much more than drink and smoke weed - pretty poor people too. they didn't like me much because i had my own car and to them that meant i was rich. anyway, they would **** with that kid sooo bad- they hit him with road cones (which hurt a lot btw and made him bleed, one kid hit him w. an ice scrapper and i saw blood squirt out his head - they called him a bit*h for going home after that, they pretty much forced him to drink , and would just mess with him really bad. eventually he moved away but once i remember he looked at me when my b/f was fu*king with him like almost to say "help me" but i never said anything for fear they'd turn on me...isn't this messed up? ever have it happen to you? is it weird this bothers me so much?