1. The the vast majority of the jokes i've seen are pretty tame, and if a guy is as big as him some light ribbing is part of the territory.
2. No matter what is going on, that guy is putting some serious work in at the gym. I'll give him credit for that. He's obviously able to work hard when he gets focused on something.
3. People get jealous, when somebody makes good money people get jealous and like to cut them down. When somebody transforms their body people get jealous and like to cut them down.
4. Like you said If he has an addictive personality, i'm happy for him if he has focused that personality on physical fitness.