The context is that Hendricks had gone hard in to the boards previous to that fight, and Polak had taken a penalty on the play. In reality he actually didn't do anything to Hendricks, he toe picked on his own. But Nurse probably didn't see a replay, and was operating under the assumption that Polak had done something dirty to him. Which is generally a pretty safe assumption, given his history. So when Polak's penalty expired, he came out of the box, was briefly involved in the play, and then went to the bench to get a change. Normally a D would not be changing at his own blue line when the play is in his own zone. Like I said, watch at around 1:15. I think that Nurse genuinely thought that Polak was skating directly towards him and challenging him for a fight, when in actuality he was skating to the bench and signalling for a change.
He's going to get a game or two, I don't think there's much question of that. But I can see why Nurse reacted the way he did, given what had happened previously on the ice, how the play developed, and Polak's reputation. I would think that there's a fair number of guys who've been run by Polak who are watching that video with a smile on their face.