plus their's the possibilitynthat the scene in question might not have even happened
Nah, that scene definitely happens because Thomas Wayne confirms it when he says Arthur must be the guy who came to his house, and little later when he says he'll kill him if he ever touches his son again.
That's another thing that separates Thomas and Murphy from Bob. I feel like people play up how villainous they both are in the movie. Yes they're both kind of douchey, but they have some justification for their behavior.
Even though he was clearly pissed off and creeped out by Arthur coming to his house, Thomas tries to be polite at first and only when Arthur keeps pushing him that's when he lets loose with how he really feels via a fist to the face and a threat. Yeah, he's kind of an asshole considering Arthur is clearly at the very least an emotionally traumatized mess, but he also wasn't prepared to meet this grungy looking unhinged man in the bathroom who came to his house the previous day, talked to and laid hands on his son, assaulted his servant, and is now saying Thomas is his dad and is refusing to listen when he explains he isn't. That's scary stalker shit that might make anyone lose their cool.
As for Murphy, as other people have said he's actually pretty nice to Arthur in person, and is actually playing off him to make his material funny at the beginning of the interview without really making him the butt of the joke. That only stops once Arthur starts talking about killing people. When you look at the type of exploitative shit on TV now, a lot of real life hosts would have treated him much worse. What Murphy did was really not any different from people having a chuckle at Tommy Wiseau, he just didn't realize how deeply messed up the weird guy he was poking fun at was. He probably even figured he was doing Arthur a favor, raising his profile in a way he could spin into a career, even if people were laughing at him instead of with him.
They both lack empathy, but neither of them deliberately torments Arthur, and only become hostile to him when provoked.
