I agree that fighting is harmful in that it can leave a player with long-term issues related to concussions, brain trauma, etc. If that's your only argument, fine.
Because he was pissed off and it was a rivalry game? I'm not sure why you think that's some sort of objective standard by which to measure fighting's impact on the game. Furthermore, as I've stated before, if you want to understand how one variable impacts another, you use science...not an interview with Claude Lemieux. Scientific research has consistently shown that fighting does not positively impact the game. The fact that a bunch of people say otherwise doesn't mean anything unless they're qualified to say so professionally and empirically. For quite a long time everybody just "knew" that the sun orbited the earth, and the world was flat. It was common knowledge...duh.
Science says fighting is harmful for the individual and unnecessary for the game. I don't really give a s*** what the athletes say. These are the same types of guys who still regularly use sterdoids, chewing tobacco, etc. They're not exactly to be trusted for their keen insights and objective thinking.
But to say a genuine fight doesn't impact a hockey game is silly. That's like saying a big hit or shot block doesn't affect the momentum of a game either. Or the crowd even. There are too many variables and differing scenarios that a scientific study won't be able to capture this.
Also, chemistry and camaraderie are vital to any hockey club. Sticking up for your linemate after a dirty hit is part of being a good teammate. You don't think that brings a team closer together?