Five little words — “I forgot he was black” — have exposed a contradiction in the idea of a post-racial nation.

The comment came from MSNBC host Chris Matthews after President Barack Obama’s State of the Union speech Wednesday.

“He is post-racial, by all appearances,” the liberal host said on the air. “I forgot he was black tonight for an hour. You know, he’s gone a long way to become a leader of this country, and past so much history, in just a year or two. I mean, it’s something we don’t even think about.”

The staunch Obama supporter meant it as praise, but it caused a rapid furor, with many calling the quote a troubling sign that blackness is viewed — perhaps unconsciously — as a handicap that still needs to be overcome.

Apparently, Matthews forgot to ask black people if they WANT to be de-raced.

“As a black American, I want people to remember who I am and where I come from without attaching assumptions about deficiency to it,” said Dr. Imani Perry, a professor at Princeton’s Center for African American Studies.

Although she thought Matthews was well-intentioned, she found his statement troubling, because “it suggests that if he had remembered Obama’s blackness, that awareness would be a barrier to seeing him as a competent or able leader.”

“The ideal is to be able to see and acknowledge everything that person is, including the history that he or she comes from, as well as his or her competencies and qualities, and respect all of those things,” Perry said.

That’s a very different vision of “transcending race” — a consistent theme of Obama’s political history — than one in which race has disappeared altogether.

“It’s important for us to remember that everyone has a race,” Blair L.M. Kelley, an associate professor of history at North Carolina State University. “When you say we’re going to transcend race, are white people called on to transcend their whiteness?”

“When (black people) transcend it, what do we become? Do we become white?” she asked. “Why would we have to stop being our race in order to solve a problem?”

Matthews didn’t get that far down the post-racial road on Wednesday night. But his comments instantly exploded online, especially on Twitter. Ninety minutes later, he clarified his comments on the air.

“I’m very proud I did it and I hope I said it the right way,” Matthews said, noting that he grew up in the racially fraught 1960s.