It's an unwritten rule in the world of sports that you don't criticize the paying fan. Take cheap shots at coaches, players, officials, media and everyone in between, but those who bear the cost of paying for a ticket are bulletproof.

An exasperated college basketball coaching icon has broken this rule in a big way.

Roy Williams lashed out following North Carolina's 90-80 loss to UNLV over the weekend in Las Vegas. The coach told listeners to his radio show that he was not pleased with the crowd near the Tar Heels bench. North Carolina fans sold prime tickets from the school's booster club to Runnin' Rebels fans.

"If you sell our tickets, your tickets that you get to the Rams Club to somebody else, and they come cheering for UNLV, I've got no use for you. And that's as blunt as I can put it. People have a right -- but not our people. You're either with me or you're not. There's no middle ground," Williams said, according to News 8 Las Vegas.

Williams had some time to cool off and change his tune, but instead he delivered the same message to reporters on Tuesday.

Follow us on Facebook and Twitter to read them first!

"Do you think ESPN likes Fox to be successful? You think Nike likes Under Armour to be successful? I mean, I'm competing out there. I don't like our fans to help the other team by either giving or selling their tickets. That's disappointing. And to do it right beside our families, you know, that's the biggest thing. And then to have somebody that's just negative, negative, negative [within] five feet of an assistant coach's wife for two nights. You know you get tired of that. But it's something that's always bothered me. It will always bother me," Williams said, as reported by Norm Clarke of the Las Vegas Review-Journal.

John Montgomery, executive director of the UNC booster club, told the Charlotte Observer that coach Williams was right to complain. "I think that's what our fans really like about coach Williams," Montgomery said.

With two NCAA championships, three Final Fours and more than 200 wins since arriving in Chapel Hill eight seasons ago, Williams certainly has the resume to bad-mouth his supporters.

And surely there are some red-faced Tar Heels fans out there holding ticket stubs from Cirque de Soleil.

Popular Stories On ThePostGame:
-- Debunking Myths About Burning Calories
-- Amazing Frisbee Throw Off Australian Bridge
-- Mariano Rivera's Mysterious Medical Condition
-- Patriarch Of Passion: How Jack Harbaugh Raised Two Of The Nation's Best Football Coaches