I've never liked rape prison jokes because it's based on a pretty disgusting double standard. It's funny if a man drops the soap but if it happens to a women, Bruce Willis needs to come and shoot those guys in the face. Again, not to say they can't be done well. Like any other joke, execution and context is crucial. But in this case, it wasn't done well at all imo. The joke was simply "Hahaha, he turned himself in prison to rape dudes, he so funny haha". Like if it made an effort of framing him in a negative light, that he was a bad person that deserved to be punished but no, he was depicted as cool and eccentric both in this extra chapter and especially in the main story chapter. Yeah he got punched out in the end but that was depicted as a bad thing, the noble hero got knocked out by the evil monster, they never explored the actions of this character as something negative, it was just thrown out there that he rapes dudes in prison and we were just expected to laugh at that. It's kinda offensive.
I'm not going to like start hating this series or anything, I still love it, it does a lot of jokes, it's going to drop the ball on one or two, that's to be expected with any series. Just saying I really didn't like this.