The thing is with fighting, the league shouldn't be held responsible if two opposing players decide to engage one another and start punching each other heads.
However, what they can do is go after the player for fighting a defenseless player who isn't in position to defend himself or doesn't want to fight.
Pretty much what the Leagues claiming tommy.... that theyve done everything they can to try & curb fighting, that fighting actually is illegal, that its the players themselves that want it & try as they might, cant be stopped, totally outlawed, banned.... To suggest that, to alibi themselves in such a manner is beyond disingenuous. Since the rise of the professional game in the early 1900's fighting has not only been permitted but its encouraged, was actually mandatory regardless of whether you were a Star Player or a Journeyman. The league promoted it, marketed it, the vast majority of the public expected it, wanted it, demanded it be part of the game. Like Boxing, unlike Basketball, Football & Baseball, a Blood Sport.
As the leading league who's actions, who's rules & culture are then emulated from elite amateur through Junior & minor-pro... woven right into the very fabric of the game in North America yes, they are culpable. To suggest that the NHL isnt responsible, well, no, sorry, thats just not on. If they wanted to stop it they could & they would. Anyone engaging, instigator, cheap shots or sucker punch's, blind side hits, even dirty stickwork... just Ban them for life. If they did that, elite amateur, Junior & minor-pro would follow suit. Fighting alone however is not entirely responsible for the epidemic of concussions thats been scrambling players brains for decades with an increase over the past 30yrs. Its the way the games played, way its taught & Coached, the NHL adding rules that rather than provide for additional player safety actually increases the likelihood of head trauma. Equipment, better training, increased size & speed, the short shift game as Dryden mentions, all contributing factors.