Last week, when White House Communications Director Anita Dunn charged the Fox News Channel with right-wing bias, Fox responded the way it always does. It denied the accusation with a straight face while proceeding to confirm it with its coverage.

Consider Fox's Web story on the episode. It quotes five people. Two of them work for Fox. All of them assert that administration officials are either wrong in substance or politically foolish to criticize the network. No one is cited supporting Dunn's criticisms or saying that it could make sense for Obama to challenge the network's power. It's a textbook example of a biased journalism.

If you were watching Fox News Channel, you saw the familiar roster of platinum pundettes and anchor androids reciting the same soundbites: this was Obama's version of Nixon's enemies list, the rest of the news media is in Obama's corner, Obama should get back to governing, and so on. On The O'Reilly Factor, Alan Colmes, the network's weak, battered house liberal, mumbled semi-agreement while "Doctor" Monica Crowley and Bill O'Reilly lit up the scoreboard with these talking points.

Any news organization that took its responsibilities seriously would take pains to cover presidential criticism fairly. It would regard doing so as itself a test of integrity. At Fox, by contrast, complaints of unfairness prompt only hoots of derision and demands for "evidence" that, when presented, is brushed off and ignored.

There is no need to get bogged down in this phony debate, which itself constitutes an abuse of the fair-mindedness of the rest of the media. One glance at Fox's Web site or five minutes' random viewing of the channel at any hour of the day demonstrates its all-pervasive slant. The lefty documentary Outfoxed spent a lot of time mustering evidence that Fox managers order reporters to take the Republican side. But after 13 years under Roger Ailes, Fox employees skew news right as instinctively as fish swim.

Rather than in any way maturing, Fox has in recent months become more boisterous and demagogic. Fox sponsored as much as it covered the anti-Obama "tea parties" this summer. Its "fact checking" about the president's health-care proposal is provided by Karl Rove. And weepy Glenn Beck has begun to exhibit a Strangelovean concern about government invading our bloodstream by vaccinating people for swine flu. With this misinformation campaign, Fox stands to become the first network to actively try to kill its viewers.

That Rupert Murdoch may tilt the news rightward more for commercial than ideological reasons is beside the point. What matters is the way that Fox's model has invaded the bloodstream of the American media. By showing that ideologically distorted news can drive ratings, Ailes has provoked his rivals at CNN and MSNBC to develop a variety of populist and ideological takes on the news. In this way, Fox hasn't just corrupted its own coverage. Its example has made all of cable news unpleasant and unreliable.

What's most distinctive about the American press is not its freedom but its century-old tradition of independence—that it serves the public interest rather than those of parties, persuasions, or pressure groups. Media independence is a 20th-century innovation that has never fully taken root in many other countries that do have a free press. The Australian-British-continental model of politicized media that Murdoch has applied at Fox is un-American, so much so that he has little choice but go on denying what he's doing as he does it. For Murdoch, Ailes, and company, "fair and balanced" is a necessary lie. To admit that their coverage is slanted by design would violate the American understanding of the media's role in democracy and our idea of what constitutes fair play. But it's a demonstrable deceit that no longer deserves equal time.

Whether the White House engages with Fox is a tactical political question. Whether we journalists continue to do so is an ethical one. By appearing on Fox, reporters validate its propaganda values and help to undermine the role of legitimate news organizations. Respectable journalists—I'm talking to you, Mara Liasson—should stop appearing on its programs. A boycott would make Ailes too happy, so let's try just ignoring Fox, shall we? And no, I don't want to come on The O'Reilly Factor to discuss it.

Jacob Weisberg is also the author of The Bush Tragedy and In an Uncertain World: Tough Choices from Wall Street to Washington.