Regardless, that idiot had absolutely no reason to intervene the way he did. And should've gotten the same knockout. The 2 guys who "had enough" sure didn't show it now did they?
Id hate to have you as a friend. You sure wouldnt have anyones back would you. Let the little guy that cant or wont fight get bullied. Just tell the bully no. Backing down and walking away from a bully makes them want to hurt you more because they see you arent going to do anything to stop them.