What joke? Having a stranger run by and grab her ass? Any man around would have bitch slapped him.
He swatted her. There was no time to "grab" anything. In context with what everyone else was doing he clearly thought he was being funny. Again she could have PRIVATELY found him and demand he apologize or else. But she throws him right to the wolves and doesn't even give him a chance to respond or apologize before he's torn apart.
He didn’t grab her ass, he slapped her ass. It’s the end of the world.