It's hard to simplify something like bullying, but there can be a pecking order involved, where people who are bullied in turn bully other people whom they feel they can influence in some way.

So, in some cases you may only need to push back to the point where you're not the easiest target in the room. ie, you don't always have to be the fastest runner to get away from animal who is looking for easy prey. You just have to be faster than the slowest runner.