Eager to forestall a U.S. intervention, Bashar al-Assad has agreed to relinquish his stockpile of chemical weapons—a stockpile that, until this week, he denied even possessing. But Syria's president continues to deny—as he did in a recent interview with Charlie Rose—that he used such weapons on civilians in an Aug. 21 attack in the Damascus suburb of Ghouta. That's less surprising than the people who believe him, despite overwhelming evidence to the contrary: countless Americans, including public figures from across the political spectrum who—out of opposition to war in general, or to President Barack Obama specifically—eagerly believe and spread misinformation. Call them chemical-weapons truthers.

One such group, Veteran Intelligence Professionals for Sanity (VIPS), which is comprised by former spooks and diplomats, last week wrote an open letter to Obama warning that he might be led by dubious intelligence into intervening in Syria. They claimed to have learned from “former co-workers” that “the most reliable intelligence shows that Bashar al-Assad was NOT responsible for the chemical incident that killed and injured Syrian civilians on August 21."

If true, this would be devastating to Obama's credibility. But skepticism of intelligence agencies notwithstanding, not everyone is likely to be swayed by the claims of anonymous informants. After all, the VIPS are also contradicting the considered judgment of the British, French and German intelligence—not to mention respected independent analysts like Eliot Higgins. Even the cautious-to-a-fault Human Rights Watch has confirmed the regime’s culpability in August's sarin gas attack.

VIPS insists its detailed account of the attack came from “a growing body of evidence from numerous sources in the Middle East.” These have confirmed, they say, that the “chemical incident was a pre-planned provocation by the Syrian opposition and its Saudi and Turkish supporters." Based on “some reports,” they allege, “canisters containing chemical agent were brought into a suburb of Damascus, where they were then opened." They forcefully reject the notion that “a Syrian military rocket capable of carrying a chemical agent was fired into the area."

I asked three of the signatories about their sources. They proved curiously evasive. But one VIPS member, Philip Giraldi, has since published an article in The American Conservative—and the reason for their hesitation has become obvious. The sources for VIPS' most sensational claims, it turns out, are Canadian eccentric Michel Chossudovsky’s conspiracy site Global Research and far-right shock-jock Alex Jones’s Infowars. The specific article that Giraldi references carries the intriguing headline “Did the White House Help Plan the Syrian Chemical Attack?” (The answer, in case you wondered, is yes.) The author is one Yossef Bodansky—an Israeli-American supporter of Assad’s uncle Rifaat, who led the 1982 massacre in Hama. Bodansky’s theory was widely circulated after an endorsement from Rush Limbaugh. A whole paragraph from Bodansky’s article makes it into the VIPS letter intact, with only a flourish added at the end.