Thing is he's done this before..
Some of his stage antics courtesy of Wikipedia (trimmed down by me.. read the whole entry for his other antics.)
On September 2, 2005, during a benefit concert for Hurricane Katrina relief on NBC, A Concert for Hurricane Relief, West was a featured speaker. Controversy arose when West was presenting, as he deviated from the prepared script. Actor Mike Myers, with whom West was paired to present, spoke next and continued to read the script. Once it was West's turn to speak again, he said "George Bush doesn't care about black people."
On November 2, 2006, when his "Touch the Sky" failed to win Best Video at the MTV Europe Music Awards, West went onto the stage as the award was being presented to Justice and Simian for "We Are Your Friends" and argued that he should have won the award instead.
On September 9, 2007, West suggested that his race had to do with his being overlooked for opening the 2007 MTV Video Music Awards (VMAs) in favor of Britney Spears; he claimed, "Maybe my skin’s not right." West was performing at the event; that night, he lost all 5 awards that he was nominated for, including Best Male Artist and Video of the Year. After the show, he was visibly upset that he had lost at the VMAs two years in a row, stating that he would not come back to MTV ever again. He also appeared on several radio stations saying that when he made the song "Stronger" that it was his dream to open the VMAs with it. He has also stated that Spears hasn't had a hit in a long period of time and that MTV exploited her for ratings.