Regardless of how much of a dick someone is off the walls, the one who covers the other is the one that starts the war on the walls, it is how it is. Not that nobody caps people because they were a dick, it can be the reason someone starts a war, but then they still start it "because" of the off-wall antics.

Besides, a bigger name like Robbo saying he hasn't heard of a (then) nobody like Banksy is normal, it's like Dolly Parton not having heard of John Moreland, but if John Moreland then replies "well I've never heard of you" back to Dolly then it's a lie or he isn't up on his history. Dolly might not slap John Moreland about it, but then again Country stars aren't literal criminals who fight over disrespect in their own city like graff writers are. Like, someone like Earsnot might have literally fought him over that tbh, like, worse than just a slap, especially back then.