Until the cup was thrown, it was business as usual in Auburn Hills.

An intense, physical basketball game; a hard foul by Ron Artest – in retaliation for a hard Ben Wallace foul a minute earlier; an angry response from Wallace; a pushing match, followed by the usual grabbing, holding and yelling as coaches and officials attempted to gain control of the situation. NBA fans have witnessed scenes like this a thousand times before.

It should have stopped there, and it would have – if a stupid fan hadn't thrown a cup at Artest, hitting him in the face.

Players are forced to endure verbal taunting all the time in sports. I once warmed up for a game at Arizona State University while two inebriated fans taunted me about the death of my father. I've had teammates endure all kinds of ugly insults, threats and barbs.

But there always has been an uneasy understanding between these idiotic fans and players that a so-called line wouldn't be crossed. Verbal assaults, ugly as they may be, were to be tolerated.Any physical acts, however, were off limits.

So when Artest was hit in the face by the cup, all bets were off. The line had been crossed, and Artest's response was understandable, if regrettable.

Imagine what any of us would do if a person showed up to our workplace, taunted us and then threw a beer in our face? How many of us would show any restraint at all?

Yes, Artest snapped, and he faces a major suspension from the NBA. So do Stephen Jackson and Jermaine O'Neal, who threw multiple punches at fans. Ben Wallace will be penalized for initiating the altercation. David Stern has to send a message to NBA players that under no circumstances will they be allowed to enter the stands to confront taunting fans, even in ugly environments like the one in Detroit on Friday night. I expect suspensions of up to 15 games for each of the three Pacers involved.

That said, I hope that each and every fan involved with the fight will be prosecuted to the full extent of the law. The fans provoked the fight, not the players. They deserve major punishment. Law enforcement officials have plenty of footage that will implicate dozens of fans guilty of instigating the brawl.

Perhaps the most disturbing shot was seeing dozens of fans showering Pacer players and coaches with popcorn, beer, cups – anything they could get their hands on as the team exited the floor. The mob mentality at that point was incredibly ugly.

Alcohol almost certainly played a role in this brawl, so I expect the league to enact rules that prohibit its sale, perhaps in the second half of games. But the bottom line is that civil behavior must prevail the next time this sort of thing becomes a possibility. Fans and players alike must show restraint, even as emotions run high and the intensity of a big game boils over.

Fans cannot under any circumstances throw anything on the floor. And players, in turn, can't respond. I expect that both the NBA and Auburn Hills police will come down hard on the participants to make sure an ugly incident like this doesn't happen again.

Steve Kerr is Yahoo! Sports' NBA analyst. Send him a question or comment for potential use in a future column or webcast.

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I totally agree with Steve Kerr and his subtext. The NBA has no choice but to fine Artest and the others, but any fan who throws something down onto a player deserves to have the crap beaten out of him. I actually support Artest's "decision" to go after the cup thrower, but he can only strike that particular fan who did it. He cannot just go into the stands and start pummeling the first guy who is too stupid to run the hell away. He has to have either seen the person do it. Or he can go up in the stands and hope some scared fans start pointing at the guy who did it. He did it. Him. Him.