A lot of times teams will have enforcers to keep other players away from the skill players. When someone goes after a skill player or hacks that player the enforcer usually comes out to 'even' things up. Why do they allow it? I have no idea. Why does baseball let their umpires get into a yelling match with players? I would assume its just the way it is. As someone else mentioned, this last week has been insane with the amount of fighting thats taken place, it is definitely not the norm.