Why does Howard Kurtz use white public opinion as the neutral baseline?

When you get past Howard Kurtz's weird obsession with Tiger Woods, and his clumsy attempts to link Woods and President Obama, there's another problem with his piece today about Obama's race.  Take a look:

I have no doubt that no matter how deep a hole Obama digs himself, African Americans, who are already the most loyal Democratic group, will remain his fiercest defenders. The latest Gallup tracking poll puts black support of the president at 90 percent -- just where it was after the inauguration. White support for Obama, by contrast, is at 42 percent.

See what Kurtz did there?  He used white opinion as his baseline.  In Kurtz's formulation, the fact that white support for Obama is at only 42 percent means that Obama has dug himself a hole. But African Americans support him anyway, despite his failings.  White support for Obama, in this construct, is the impartial baseline against which Kurtz assesses Obama's "true" performance as president -- he has dug himself a hole.  And since African American opinion of his performance doesn't reflect that "true" assessment, African Americans will fiercely defend Obama no matter what.

Kurtz's formulation is simply a subtler version of Chris Matthews' tendency to use the phrase "regular folks" when he means "white folks."

Later, Kurtz wrote:

[T]his is a striking formulation:

"The only thing I cannot do is, by law I can't pass laws that say I'm just helping black folks. I'm the president of the entire United States. What I can do is make sure that I am passing laws that help all people, particularly those who are most vulnerable and most in need. That, in turn, is going to help lift up the African American community."

In other words, Obama argues, good politics generally is good black politics as well.

Well, no.  Obama is talking about policy, not politics.  It isn't surprising that a Washington Post reporter would conflate the two, but it is disappointing.