Because they prolly went home and took it out on the dog, or beat their wife/kids or picked up a fight in the club/bar/gym for a non-issue. You can see these people coming from miles away.

It's not very hard to see the difference between someone starting a fight to sort something out VS someone starting a fight just for the sake of fighting and to let off some steam.

People can only swallow their self respect and pride for so long, and it's only a matter of time before the craving for respect and appreciation spills over to other aspects of their life.