Also keep in mind that many bullies come from really shitty backgrounds and their behavior is a projection of their own problems. Most deserve to be pitied, not obliterated, not that that makes life as a bullying victim any easier to deal with.
I always wonder exactly how this story started, but it's got 90's written all over it. Sure, such hardluck cases exist. I remember one guy in middleschool who liked to brag about shit his brothers (plural) taught him about being in jail and shit.
There's also a pretty strong strain of whitebread bullies who've had everything handed to them in their lives and never heard the words "no" or "stop that", so whether consciously or not think they're entitled to push people around. Or the strain I got to deal with in my school district, which saw an unstable mix of genuinely impoverished black and hispanic students, and painfully wealthy white kids trying desperately to be "gangstas", turning into vastly bigger dicks than it would have ever occurred to their real-world counterparts to be.
Self-esteem is such a skeleton-key of child psychology it's a joke. As George Carlin once put it, it turns out that successful motivated violent people think very highly of themselves.