As Fox News celebrates its 10-year anniversary, media watchers should appreciate how Fox, which tilts right, has provided balance to major new operations such as CNN and The New York Times, which tilt left.

Go to most newsrooms and you'll find a staff that overwhelmingly voted for John Kerry in 2004, while the rest keep their politics to themselves lest they be considered biased. A survey of the Washington press corps found that 89 percent voted for Bill Clinton in 1992. It's true, most reporters do their level best to tell a story straight and present both sides. To use Fox-speak, most reporters I know strive to be "fair and balanced."

But they can't escape the presumptions that underlie their stories, and they are likely not to notice the presumptions when all the newsroom management thinks alike. That's how illegal immigrants became "undocumented workers" and global warming became a certainty.

Sometimes you'll see journalists talk as if opposition to same-sex marriage or support for the death penalty is a Republican position -- even though the liberal electorate of California supports the death penalty and voted to ban same-sex marriage. You see, the journalists are liberal, against capital punishment and for same-sex marriage, so they automatically assume that people who disagree with them on those issues must be Republicans.

The worst of it is: They have no idea that they're biased. They think their positions are neutral. New York Times court reporter Linda Greenhouse provided a perfect example last month when NPR broadcast remarks she made during a Harvard speech. Ignoring a Times rule that prohibits reporters from publicly stating personal views that could not run in stories, Greenhouse bemoaned the Bush administration's creation of "law-free zones" at Guantanamo, Abu Ghraib and Haditha, "the hijacking of public policy by religious fundamentalism" and the "ridiculous" proposed fence on the Mexican border.

Some might argue that the Times policy is silly, as all reporters have opinions. The paper's public editor, Byron Calame, argues that the rule demonstrates "a determination to be an impartial observer by keeping personal opinions separate and private -- not pretending they don't exist."

I am struck by the fact that Greenhouse, who parses Supreme Court decisions for America's paper of record, told Calame the Harvard remarks were not her opinion, but "statements of fact." If Greenhouse cannot distinguish between fact and opinion, why should I trust her reportage on court decisions? Continued...