You, and everyone, who compares this to being attacked on the street is making one big mistake. This was not to random individuals on the street. This was at a place of work with security. To me it is more like a courtroom. Where defendants have attacked people before. Ususally, the Judge does not fly off his chair, but leaves it for a bailif to restore order.
Being hit by a half empty cup, when there is securty, is not a cause to attack someone. Artest could have had that fan ejected and arrested. Instead he over-reacted, and escalated the incident. For any fan other than the beer thrower, to have a NBA player charge into the crowd near you, and have no idea who he is planning to attack. I am surprised they did not take Artest down as a group. Simple, in this case, Artest was not under any threat of being further assulted. He chose to go into an opposing crowd to meed out some street justice. No matter what he had hit in that crowd, he was wrong.
As for Ben Wallace, yea his action were bad, traditional basketball bad. Give him his few games. His actions were within the game. Artest attacked paying fans who had nothing to do with the beer. That is unjustifiable. His mistake is not justified, because it was not reasonable or necessary for him to defend himself from a 1/2 empty plastic cup.
That's not true though. Even when the game was called off and the players were making a hasty retreat to the locker room the fans were busy pelting them with more cups filled with beer and other objects. Security was doing nothing to stop the further assaults on the players.