Yes, the fan should be banned from games if that's what he said. Marcus should also be kicked off the team regardless.
As bad as a racial slur is, it isn't an excuse to assault someone.
If that's what the guy said, which I have no doubt it was, then he deserved a lot more than getting pushed back into his seat, lol. It's up to the individual whom the racial slur was used against whether or not it's reason enough to assault the instigator, imo...
A reporter from the oklahoman last night tweeted that the fan actually texted a friend (who shared it with the reporter), that he "may have gotten carried away," and "said some things he shouldn't have." So, I think the fan knows he's (the fan) an idiot and is rightfully trying to accept responsibility for the whole thing so that he won't catch the backlash if Smart is suspended.
I suspected a racial slur was the cause initially, but I still felt that Smart had to walk away from that. Now KNOWING that the slur was indeed the cause, while Smart shouldn't have retaliated or even acknowledged the idiot fan, he should not be held responsible for his actions. John Lucas III also tweeted last night that he remembered that same fan from taunting him during his college years and then there's video of the guy flipping off an A&M player while at the FT line... He deserved it.