They've cleared the dugouts twice already, and Pedro threw Zimmer to the ground. Zimmer tried to attack him, so I guess Pedro was acting in self-defense.
Pedro was pretty much protecting himself from Zimmer. It was a shame to see Zimmer tossed to the ground, but he did it to himself. I'm not sure what (or if ) Zimmer was thinking.
Tim McCarver acted like Pedro was unbelievably wrong to defend himself. But he is so biased toward the Yankees that his reaction was not unusual.