Slicing and dicing

In "The Audacity of Hope", the 2004 Democratic National Convention speech that vaulted him into the national attention, Barack Obama said this:

Now even as we speak, there are those who are preparing to divide us -- the spin masters, the negative ad peddlers who embrace the politics of "anything goes." Well, I say to them tonight, there is not a liberal America and a conservative America -- there is the United States of America. There is not a Black America and a White America and Latino America and Asian America -- there’s the United States of America.

The pundits, the pundits like to slice-and-dice our country into Red States and Blue States; Red States for Republicans, Blue States for Democrats. But I’ve got news for them, too. We worship an "awesome God" in the Blue States, and we don’t like federal agents poking around in our libraries in the Red States. We coach Little League in the Blue States and yes, we’ve got some gay friends in the Red States. There are patriots who opposed the war in Iraq and there are patriots who supported the war in Iraq. We are one people, all of us pledging allegiance to the stars and stripes, all of us defending the United States of America.

In the end -- In the end -- In the end, that’s what this election is about. Do we participate in a politics of cynicism or do we participate in a politics of hope?

So how right is he? Show me one national media outlet that's not slicing and dicing the electorate into conservatives, independents, liberals, white, black, hispanic, men, women, rural, urban, heterosexual, homosexual, blah blah blah etc. Astounding. Have "they" (we) been doing this all along? Why hasn't someone pointed this out before? Is it harmful?