Was it because Patton was already seen as someone who needed to be taken down a peg or two and this was the perfect opportunity to do so?

Was slapping soldiers out of combat seen as a big no no (I imagine slapping them, kicking them in the backside, etc were done all the time in combat to get them out of ditches, get them moving, etc)? I'd think it probably wasn't the only time an officer had hit a soldier he thought was a coward.

Was there a level of sympathy for the slapped soldiers due to one of them turning out to be quite ill and the other had requested to be allowed to return to his unit before Patton's arrival?

Is it something I'm missing?