Then again, maybe he's just burnt out from running these sites and this was the final straw. I can understand if he wants to pack it in after so long, and this is as good reason as any to call it a day.
Though, has no-one in that community offered to take over? Forums do change hands now and then.
As the manager of a community where people meet in person, I understand where he is coming from. Acting like law enforcement puts one in a position to confront dangerous individuals without authority or weapons. It is literally life-endangering.