Artest was getting shoved by Wallace, and Wallace was continualy trying to get at Artest, throwing a towl at him. If you were in that situation, that'd get you going. Artest knows what people think of him, and what kind of situation he was in. He tried to stay away from it, laying down on the press table. However, the throwing of the beer didn't help.
I guarantee if all those things were going against you, you'd done the same thing.