OK, just talking to the pieces... Wilson definitely grabbed the hair and pulled him down by it to force his head back and direct all of his weight arched backwards. There is no other reason the head is straight back that way, and certainly no hockey player would do that to himself in a conflict situation. Forcing him to the ice from that point was intent to injure. Just my two cents. If the DoPS doesn't see a suspendable offense there, then the league has a problem. Lot's of stuff happens in scrums, but attempting to slam the head of another player into the ice isn't/shouldn't be commonplace.
Separately, if the league wants stuff like this to cease then there are a couple of ways that are meaningful. You suspend the coach to match the player suspensions in some sort of ratio - maybe 25% of the player suspension. Further, you don't allow the team to replace the player on the game day roster for the length of the suspension (not to exceed say 7 games). So the Caps are down a player each night that Wilson is suspended after the Carlo hit. It forces the team to enforce accountability on the players. Finally, in the case of the suspendable act resulting in an injured player, you don't allow the player to return to the ice until the player he has injured returns. You need some league Dr review/involvement and some "not to exceed" language to make sure that no gamesmanship happens - but if Carlo misses 15 games with a concussion on a suspendable hit, the player that intentionally causes it shouldn't be on the ice either.
It's not perfect, but create a system where the coach AND the peers have a vested interest in the player behavior, and punish the crap out of the schmuck who tries to make a career out of injuring other players. Because as it stands right now, Wilson is grinning knowing that he can do exactly the same garbage to another player next game. The fact that Wilson is willing to answer the bell for his schmuck stuff doesn't mitigate the behavior when it is intent to injure IMO. I'm with some of the others above (since the league has decided it's acceptable) one of Wilson's teammates is going to catch a beating or a vigilante act with the message "tell Wilson he's the one that caused this". That isn't desirable, but it'll happen. Maybe not because of this incident... but for these kinds of incidents (with weak response by DoPS).