McClurkin is a guy who claims to be "ex-gay" and is a Gospel Singer who was on Obama's "Embrace the change" tour in South Carolina.
Before the tour, the story broke that McClurkin said things like "Homosexuality is a curse", "Gays are going to kill our children", etc. Several Gay civil rights groups then asked Obama to bump McClurkin from the tour, Obama refused and said the guy was "only going to sing". As a concession, Obama put one pro-GLBT minister on the roster to speak before the concert began.
During the Concert, McClurkin was the Master of Ceremonies, and towards the end he had a half hour to preach his hatred of GLBT people, and proclaimed that "God saved me from Homosexuality".
Afterwards, Obama said that he disagreed with McClurkin, and even worse, like this:
The concert was to be the highlight of this outreach and while the crowd left excited, it was clear the campaign still regarded the controversy as complicated. Aides gave reporters a three-page memo detailing McClurkin's and Obama's views on gay rights that noted in capital letters "MCCLURKIN DOES NOT WANT TO CHANGE GAYS AND LESBIANS WHO ARE HAPPY WITH THEIR LIVES AND HAS CRITICIZED CHURCH LEADERS WHO DEMONIZE HOMOSEXUALS," with quotes detailing those statements from the singer.
The next paragraph then stated "OBAMA DOES NOT AGREE WITH MCCLURKIN'S VIEWS ON GAYS."The caps lock is in the original Washington Post Article, here:
http://blog.washingtonpost.com/the-trail/2007/10/29/post_159.html