MSNBC host Chris Matthews is under fire for commenting on air that President Obama has done so much to heal racial divides that "I forgot he was black" as he watched Obama's first State of the Union address Wednesday night.

Matthews, who appeared on the cable network shortly after the speech, said of the president:

"I was trying to think about who he was tonight. And uh, it's interesting. He is post-racial, by all appearances. You know, I forgot he was black tonight for an hour....

"I was watching, I said, 'wait a minute!' He's an African-American guy in front of a bunch of other white people and there he is president of the United States and we've completely forgotten that tonight -- completely forgotten it!"

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Matthews' remarks came as he was praising the president for working to heal racial divides and for delivering a State of the Union address that he described as "profound" and "so in tune with so many problems and aspects of American life."

But the "I forgot he was black" remark quickly set the blogosphere on fire, as hundreds of viewers questioned the meaning and implications of Matthews' words.

"For his idiotic racist comment last night, will Chris Matthews be flogged and pilloried like Imus was?" tweeted "Shoehead."

"When I 1st heard what Chris Matthews said I thought maybe Pres Obama just looked extremely light-skinned 4 some reason," tweeted "QueenMelmendi."

Brent Bozell, founder and president of the Media Research Center, a conservative media watchdog organization, said the remarks reveal a prejudice on Matthews' part.

"What Chris Matthews is saying is that he doesn't believe African-Americans are capable of giving speeches like that."  

He said Matthews' remarks "show the absolute contradiction in the liberal argument on color. They purport to want a color-blind society, but are absolutely fixated on doing just the opposite. [Matthews] can't see Barack Obama as being qualified, because he's Barack Obama. He sees him through a lens of being black."

An MSNBC spokeswoman did not reply to a request for comment.

Controversial remarks are not new to Matthews. The on-air host was roundly criticized for calling West Point cadets "the enemy camp" when Obama spoke at the U.S. Military Academy in December.

Matthews also was criticized for saying he "felt this thrill going up my leg" after listening to Obama speak during the presidential primary campaign.