Kopitar was cussing going off the ice, Kopitar is not a guy who complains about refs call.
It was a weak call.
Oh...so because Kopitar is cussing and as you say, that he never does , it's a weak call...first of all Kopitar is a human being, not a robot, so his attitude will change depending of the circumstances and it could very well be that he was mad at himself for taking a penalty so close to the end of regulation. Second, look at the play, he put his arms around Perry and brings him down, in the NFL it's a tackle, in the NHL that's holding 100% of the time.