Schools will eagerly put in place various other zero-tolerance policies, like no fighting. So if you dare defend yourself against such a social predator, you are taught a lesson by such a policy that you've done a bad thing.
I was fortunate never to be a victim of bullying, but many of my friends were (we were a bunch of nerds after all). The difference was I had support at home for fighting back because my parents knew the administration wasn't watching out for students well being. The lesson I learned is that fighting back is the single most effective strategy for stopping bullies, and that parents have to ensure that their child is shielded from ineffective school behavioral policies.
My friends didn't have such support and suffered from it, and couldn't ever learn that lesson. Some of them couldn't have fought back even if it was okay for them to do so for various reasons. The ones I still have contact with today have lingering social problems from the childhood bullying and this has fully reinforced on me that bullying is a social plague that needs to be aggressively stamped out.
There is the other side that bullies themselves are suffering in turn. Many come from shattered home lives or abusive parentage. Those children should be identified and put into some kind of counseling program as early and as intensively as possible. They will also grow up to be damaged in some way because of it and in their lives, perhaps only the school has an opportunity to tamper down their violent instincts.
However, the physical and emotional violence that bullies subject others to is absolutely not to be tolerated in any way. And it seems the best way for other children to handle it is to simply do their best to fight back.