It's an interesting question, for sure. I think we need to remember that the NHL is a business for making money, and people enjoy watching fighting while they're at the games. The negative side of that is that it really makes an impression on the younger players, and so forth.
I think that when rules in younger leagues are allowed, such as all the bodychecking—just because that is what I know most—it sort of changes the mindset of the players. Rather than going for the puck, they're just going to make the hit, and then it turns into a competition between the friends of who can have the biggest hit and so forth.