I'm going to let a student get away with some justified bullying
You want a kid to bully the bully?
He's just a young and stupid kid and behaves like any other 15-year old.
You should alway stand up to bullying since it's never justifiable. Bullying is simply wrong and for you to not care about it tell me you are also part of the problem.
I don't have time to deal with all this drama, but let the kid be.
Bullying as a form of retaliation won't solve anything. Address the issue head and on arrange for a meeting with the kid and the parents. See if you can come to a reasonable compromise.