Any baseball fan knows, do not mess with Boston Red Sox fans, especially not on their turf.

President Obama may not have known what he was in for Monday night in Beantown, where at a fundraiser he thanked the crowd for a recent trade between the Red Sox of Boston and his hometown White Sox of Chicago. "Boston, I just want to say thank you for Youkilis," Obama said at Symphony Hall, "I'm just saying, he's going to have to change the color of his socks."

The president was referring to Kevin Youkilis, a slugger and favorite among the ‘Red Sox Nation,' who was traded this week to President Obama's favorite team, the Chicago White Sox. Obama's Boston supporters responded with chants of "yook" which was interpreted by some, as "boos", including the president.

"I didn't think I was going to get any boos out of here," Obama said. "I should not have brought up baseball. I understand. My mistake. You've got to know your crowd."

Former Massachusetts Governor Mitt Romney didn't miss the opportunity to attack the president's remarks. "In baseball, an error is a misplay or fumble, as when a player drops a pop fly or lets a ground ball go through his legs. Last night in Boston, President Obama went to the heart of Red Sox nation and committed an error by taunting fans over the Kevin Youkilis trade to the Chicago White Sox," Romney campaign spokesperson Andrea Saul said in a mail to reporters.

"Maybe the President should have congratulated the team for winning the World Series in 2004 and 2007. Instead, he chose to mock them for trading away one of its favorite players at a time when the team is struggling," Saul's note continued.

The president's own press secretary Jay Carney, an avid Red Sox fan, defended the president's remarks. "He is a White Sox fan, he owns his fandom of the White Sox . He proved that again last night," Carney told reporters Friday. "And anyone who knows Boston, knows the Red Sox and anyone who was ,in that room last night knows that the preponderance of people shouting in response to what the President said about Kevin Youkilis were saying ‘Yoooook and not Booo' ‘Yooook' and not ‘Booo' for God's sake."

Carney referenced a 2007 occasion when Obama was campaigning for president, he declined to wear a Red Sox cap at Fenway, refusing to stray from his alliance to the other Sox. "I don't think the American people appreciate it when politicians suddenly pretend they are fans of other teams to a curry favor. The president is very serious about his sports teams, he will not do that. He will not cross that line," Carney said.

The Minnesota Twins defeated the Chicago White Sox 4-1 in Youkilis' debut game Monday night. The Boston Red Sox also fell to the Toronto Blue Jays Monday night, 9 - 6.