That viral video, "gangnam style" launched south korean rap sensation psy into the spot light. Tonight, his lyrics from years ago and anti-american words are causing anger here at home, just as he prepares to perform for the president. Here's muhammad lila. Reporter: Call it controversy, "gangnam style." Long before it sparked a dance craze, he performed at a politically charged concert in 2004 with anti-american sentiment running high after a korean missionary was killed in iraq. He sang these lyrics. Kill those bleeping yankees who have been keeping them hostage. Kill their daughters, mothers, daughters in law and fathers. If you were thinking of horrible things that could get pop stars in trouble, you would have a hard time coming up with worse things than this. Reporter: Many fans are reacting with fury, saying spy should not be able to headline the christmas in washington concert on sunday. This is not the first time an artist has courted a political controversy. But this is different. Spy is so popular. His youtube video is the most watched of all time. It was social media that helped make his career. Now it's social media that could break it. Even after psy apologized, saying it was a deeply emotional reaction and said he will forever be sorry for the pain he caused, there are still negative twitter posts. The white house says the concert will go on and president obama will attend, saying they have no control over who performs at the concert. The anger is exploding. Thank you to you tonight.