attack-dog
Rick wasn't like Lee. Lee listened to Rei, and Rei was blinded by proximity, so Lee's hands were tied. But Rick didn't listen to Max; he had a greater authority, without vested interests in the well-being of Kai. His authority only had vested interests in the well-being of Max, and it directed him towards that goal. And really it wasn't difficult to conclude that Kai threatened this end.
He was always hurting them. Particularly Tyson, who then took it out on his friends. And this hurt Rei, of course, and Lee didn't like it but his hands were tied. And that was a factor, of course, but more importantly Tyson's outbursts hurt Max. And it wasn't Tyson's fault—he'd always feel so sorry—easily it was Kai, who never felt sorry, who was the CORE ISSUE.
And Rick told him so, slamming him against the wall. And it was in Rick's eyes, "Don't think I won't do anything. I'm not Lee." And Rick had to hurt him; he answered to a higher authority than Tyson, pulling at his hands choking Kai. He answered to an authority higher even than Max.
And that authority had concluded that Kai was the problem.