It's an endless cycle. With each generation, there is at least 1 or 2 bullies. Sometimes those bullies will grow out of it once they mature and realize what a butthole they've been. Once in a while the bully will stop because the person they've been bullying stands up to them at some point. Some of the bullies won't grow out of it and will grow up to be bullies as an adult because they don't see anything wrong with their actions.
Anyway, this movie should be a lesson to people that are bullies. If you are going to be a bully, don't be surprised when you invite some bad juju into your life and something bad happens to you.