See, my sexually-deprived animals are all pretty sweet. Even the biters turn sweet when the hormones kick in, I guess because defensive striking at everything that moves doesn't really impress the girls.
Most cage aggression is associating the handler with food. Is he eating? If he's eating, it's a feeding response. If he's not, then I guess we're back to some kind of stress.
You know? I think this is one of those rare cases where you might want to consider moving a snake back to a glass tank. I'd definitely consider feeding him in a cardboard box instead of the tub/tank for a while.