The (Liberal) politics of race.

Liberals have grown up with assumptions implanted in their heads, assumptions that they regard as facts. For example, in the Liberal mind it is assumed that blacks are poor and underprivileged, while whites are rich, well-connected insensitive authority figures. I am indebted to Juan Williams for pointing out that in the "Gates gate" the privileged authority figures were black (Cambridge has a black police chief, black mayor and the State has a black governor) and the policeman in question is white. Even the woman who reported what she believed to be a break-in was not of a privileged class, but of Portuguese descent.

Some, such as the Editor of the W Times believe that Gates simply responded as an overpampered, privileged Professor of Harvard, whose hubris is rubbed by a mere Irish cop not being deferential to him:

http://www.washingtontimes.com/news/2009/jul/28/a-teaching-moment-in-class-warfare/?feat=article_top10_read

But again I must go with Juan Williams: Obama acted the way he did because of the 20-year influence of the Reverend Wright. If you listen to anti-white rants for 20 years, it rubs off on you. And Obama acted on the basis of his assumptions. Which were wrong. End of story.