If "the truth has a well-known liberal bias," as liberals are fond of saying, then you have to wonder why some of them feel compelled to embellish it.

Granted, conservatives and other non-liberals are not exactly allergic to what Stephen Colbert, the much-lionized author of the aphorism above, calls "truthiness": the quality a belief has of feeling it must be true, even if it isn't, because one so badly wants it to be true. Many conservatives seem all too eager to believe that President Obama is a closet Muslim who was born in Kenya; that America was founded as a Christian nation; that Saddam Hussein was stockpiling WMDs; that climate change is nothing but a liberal lie; and so forth. Fox News embarrassed itself just the other day with a claim that Birmingham, England, was off-limits to non-Muslims.

Some conservatives believe such things in good faith, in the sense that they have rationalized away evidence to the contrary and sincerely think they are right. But others lack even the weak defense of confirmation bias. Some years ago the now-defunct Global Climate Coalition, an industry-funded group, publicly insisted that "the role of greenhouse gases in climate change is not well understood"—even though a report for its own internal consumption conceded that "the scientific basis for the Greenhouse Effect and the potential impact of human emissions … on climate is well established and cannot be denied." The group's leaders were lying to the public, but not to themselves.

***

The latest manifestation of such mendacity goes by a different name: Jonathan Gruber, the MIT economist who was caught on video conceding that the Affordable Care Act was written "in a tortured way" to prevent the Congressional Budget Office from spelling out its true costs. "Lack of transparency is a huge political advantage," he said, because of "the stupidity of the American voter." In other words, the architects of Obamacare, including Gruber, knew telling people the real price would keep it from passing.

In that instance, the truth had a clear conservative, or libertarian, or at least non-liberal bias. Ditto for President Obama's frequently repeated claim that if you like your health care plan, you can keep it. This turned out to be false for a large number of people, and wound up as PolitiFact's Lie of the Year for 2013. All of which makes you wonder: If the ACA was such a wonderful piece of legislation, then why such great need to lie about it?

If non-liberals fall prey to truthiness, then liberals fall prey to FBA: "fake but accurate." That was how The New York Times described a set of memos, publicized by CBS, ostensibly impugning George W. Bush's service in the Texas National Guard. By a remarkable coincidence, the memos surfaced in the heat of the 2004 presidential election. They turned out to be fake, but they said things liberals were eager to believe.

For a long time Neil deGrasse Tyson, the popular astrophysicist, told another fake-but-accurate story about Bush, which illustrated both Bush's ostensible stupidity and his ostensible religious bigotry. As Tyson told the tale, in the wake of 9/11 Bush—wishing to distinguish Christians from Muslims—said, "Our God is the God who named the stars." When challenged late last year, Tyson defended the quote, claiming he had an "explicit memory of those words being spoken by the president." Eventually, Tyson conceded his memory was faulty and backed down.

Tyson's story had a grain of truth: Bush had said something about a God who had named the stars, but he had made those remarks in a vastly different context: the explosion of the space shuttle Columbia. In the wake of 9/11, Bush stressed that Islam was not America's enemy. But those truths were less politically satisfying than the truthier version Tyson told in speeches.

***

There also was a grain of truth to the church-burning scare in the late 1990s. After several predominantly black churches in the Southeast burned, civil-rights leaders and the media suspected a racist plot.

"There's no question in my mind that there's a conspiracy," said Spiver Gordon, a leader of the Southern Christian Leadership Conference. When a Justice Department investigation found no conspiracy, activists said that made it even worse: The spike in arsons was being fueled by a general atmosphere of racial hostility in the country at large. The panic inspired a radio address by President Clinton and state legislation imposing stiffer penalties for arson.

A national task force was convened. Just one minor detail was overlooked: Over the previous two decades the frequency of church arson actually had fallen by almost two-thirds. Heaven knows America was not free of racism by the late 1990s. Yet the media credulously reported a church-burning epidemic because the reality was not good—or, in this case, bad—enough.

Other media embarrassments have occurred after various outlets attacked other stock villains in the liberal narrative. The San Jose Mercury News blamed the CIA for the crack cocaine epidemic, then had to back off the claim. CNN and Time magazine had to retract coverage claiming the American military had used sarin gas to kill defectors during the Vietnam War. NBC's "Dateline" had to apologize to GM for staging an explosion in a truck's fuel tank. The Cincinnati Enquirer had to apologize to Chiquita for accusing it of nefarious business practices. ABC had to pay more than $5 million to Food Lion for a story about "'what can happen when the pressure for profits is great and you break the rules," as Diane Sawyer put it. Examples multiply.

When it comes to the truth, the real bias is thinking any one side has a monopoly on it.