The back of my ticket states:
"The holder of this ticket voluntarily assumes all risks and dangers incidental to attendance at this event, including the risk of lost or damaged property or personal injury of any kind, whether occurring before, during or after the game. It is understood that the license granted by this ticket is for the purpose of viewing the game as an eyewitness only."
Seems pretty clear to me.
This just clears the venue of liability if someone gets hurt at the arena, it doesn't justify getting punched by a thug who can't handle losing.