Unfortunately, the bully would have to admit that this is what they are. Sadly, denial happens. No one really knows what goes on inside the heads of bullies to truly understand why they do the things they do. And actually, there are anger management programs that could possibly help. But that crucial first step is in getting the bully to admit that he is one and then further convince them that they need help.
Disclaimer: I am only responsible for what I say, not what you choose to understand.