Over the past week, Fox News has aggressively rebutted accusations that its star host Bill O’Reilly lied about his whereabouts during the Falklands War in 1982. But after a new report challenged O’Reilly’s recent claim that he was present at the violent suicide of a Lee Harvey Oswald acquaintance in 1977, the network declined to defend him. Is Fox blinking?

The new charges, which were first aired in 2013 by the website JFKFacts.org and further corroborated in a new report by Media Matters, concern George S. de Mohrenschildt, a Russian geologist who became friends with Oswald’s family in the early 1960s; he killed himself with a shotgun at his home in Palm Beach, Florida after the House Select Committee on Assassinations asked him to testify about his ties to Oswald.

In two recent books recounting his experience as a young reporter covering President John F. Kennedy’s death for a Dallas television station, O’Reilly claims he was standing on Mohrenschildt’s front porch when he pulled the trigger: “As I knocked on the door, I heard a shotgun blast. He had killed himself.” He has repeated this story during at least one Fox News segment. But two of O’Reilly’s former colleagues told Media Matters that he was actually in Dallas, not Palm Beach, on the day of Mohrenschildt’s death. Their claim is supported by several other official accounts, including a lengthy police report submitted by the Palm Beach County Sheriff.

In other words: O’Reilly’s story, intended to portray him as an enterprising journalist unfazed by potential danger, is a fiction. It is precisely the sort of claim that would otherwise earn Fox’s condemnation, and draw sophisticated counter-attacks to undermine the accusers’ reputation.

Yet in the 20 hours since Media Matters posted their report, Fox News has either refused to comment or directed questions to O’Reilly’s book publisher. This response is telling. The network immediately dismissed allegations that O’Reilly fabricated his account of reporting on the Falklands War, and even let O’Reilly brand one of his accusers, Mother Jones reporter David Corn, as an “irresponsible guttersnipe” and a “far left zealot who has attacked Fox News many times before.” The network’s senior executives, including Roger Ailes, said they were fully supporting the host. This line of attack worked so well that media reporters quickly declared victory for O’Reilly. Not because he hadn’t lied—he had—but because he’d successfully portrayed his critics as shifty liberals desperately trying to smear him.

But neither Fox nor O’Reilly have attacked Media Matters or even questioned their reporting. And the thing is, Media Matters is far more ideologically aligned against Fox News than Mother Jones or David Corn. Founded in 2004 by Clinton ally David Brock to combat conservative misinformation,” the non-profit press watchdog has since focused its efforts on subverting Fox’s right-wing narratives. In 2011, Brock told Politico that his organization would engage in “guerrilla warfare and sabotage” against the network, which remains the dominant cable news outlet in the United States. In return, Fox aired dozens of counter-attacks on Media Matters and even called for the I.R.S. to revoke its tax-exempt status.

Today, however, Fox News is declining to defend its most valuable asset from an organization dedicated to its destruction. O’Reilly might want to ask his boss about that.

Update, 5:40 p.m.: Two hours after this post was published, Fox provided the following statement to Mediaite (without addressing the substance of the Media Matters report):

Bill O’Reilly has already addressed several claims leveled against him. This is nothing more than an orchestrated campaign by far left advocates Mother Jones and Media Matters. Responding to the unproven accusation du jour has become an exercise in futility. FOX News maintains its staunch support of O’Reilly, who is no stranger to calculated onslaughts.

Okay then.

Email the author: trotter@gawker.com · Photo credit: Getty Images