Would you getting fired make the asshole stop? If so...
Get one of your supervisors to contact the guy and lie to him that you have been fired, take on a new username and stop posting non-anonymous stuff with it.
We are known locally and everywhere else for our political corruption. I think it extends way past politics though. I have lots of local connections – the "I'll scratch your back you scratch mine" mentality is strong around here. I would be shocked if we were unique for it, but it seems to be a common feature of the land.
Get one of your supervisors to contact the guy and lie to him that you have been fired, take on a new username and stop posting non-anonymous stuff with it.