Rick's Mean Streak
For such a laid back guy, Rick can fly off the handle pretty easily. It's apparent in a few scenes in the film: with the punks on the beach, the art collector, and his reaction to his car salesman friend when he brings up what his boss said.
Thinking about it now, I think he gets that anger from his father who showed he has this same trait by blowing up at Rick during the dinner scene at the house.
Like father, like son.