That's the thing about deterrence. Having a guy who can beat someone senseless isn't deterrence. Now, convincing the other team you have a guy who absolutely will destroy your star player if you cross a line, that is deterrence.
As much as I may have a soft-spot for KMac, he's not really deterrence, he isn't the type to fight a smaller guy and I've not seen him target anyone successfully with a check to this day. Now Steve Downie on the other hand... he was capable of deterrence. An absolute mad-man, and everyone knew it.
But it's not deterrence, because "deterrence" is a myth, at least when it comes to players "policing" themselves. You really think the Jets "learned their lesson" with Hartman's gesture and subsequent explanation? I promise you they didn't, they'll simply come back even harder the next time they square off. "Deterrents" don't deter violence. They escalate it. Not only are they horrid at their jobs, they rely on the very notion of doing the exact opposite to perpetuate that myth and stay employed. How many teams has Ryan Reaves told that he's the solution to their Tom Wilson problem, when he very obviously wasn't?
Same goes with Downie, he didn't deter shit, he was a helmet-kicking shit-disturber in the same vein as Radko Gudas, and he's since been pretty outspoken about how wrong he and meathead hockey culture are.
There is one and ONLY one deterrent in sports. Suspensions. That's it. The NBA doesn't have a violence problem. Why? Because when something bad happens they bring the hammer down. HARD. Carmelo was involved in a scrap and IIRC got 10 games. He never did it again. But hockey still thinks they need the extracurriculars to sell the game to Neanderthals who still think the game would be better if it were played without helmets.