I'm glad that punching back worked out for some kids, but I would be wary of inferring a general rule from that. Might be the kids for whom punching back didn't work out just didn't tell their story.

What could also happen is that the bully gathers his friends and strikes back in a big way. Or maybe he has a knife. Or whatever - I don't know, probably I would try to punch back, too. But I don't think it is essential for people to go through such an ordeal.