Here's a little friendly advice from me to you... be nice to that guy, be very very nice to that guy... that way, once the day finally comes that he decides to walk in with semi-automatic weapons and level everyone in your gym, he may remember that you were nice to him, and let you live.
Once upon a time, I was a retail assistant manager, and we had an employee that was really strange, just an odd ball that was a bizarre dude who would talk to himself outloud. He was often late and would leave without completing his duties. This would piss me off, so one day I barked at my boss "why do you let this piece of shit get away with this crap and do whatever he wants to do? Are you afraid of him? You're the boss!"
My boss turned and said "God Bless it, I'm just trying to stay off of his list - you know, the list of people he plans to kill that he is probably keeping on his refrigerator?!".