Aizawa knows the bullying is happening. He has nothing to do with it, but he's not going to step in until the daughter personally comes to him or somebody else for help.
He's pretty much doing this to get back at his bully and have what he said about "those getting bullied not deserving his...
I'm going to go out on a limb and guess that it's going to be his childhood friend that ends up being the sanest person in this town despite how much of an ass he is.