I understand they aren’t supposed to take their helmets off before the fight, but just let them take whatever the punishment is for doing so. If the league doesn’t think the punishment is strong enough to dissuade the action, go ahead and change it.
All this being said, if two guys do take their helmets off, the linesman should absolutely not be chasing players around the rink. You can’t tell me the increased risk of injury from taking off a helmet for the players is greater than the risk of two guys trying to intervene in the middle of fists being thrown.