INVENTED TRUTH and projection bias: I forgot I was white.

The "I forgot Obama was black" sentiment allows the speaker the comfort of accepting, even lauding, a black person without interrogating their invented truth. It allows the speaker a luxurious ignorance--you get to name people (this is what black is) even when you don't know people. In fact, Chris Matthews didn't forget Barack Obama was black. Chris Matthews forgot that Chris Matthews was white.

Link from the Washington Times.