“If I brought down the Mob,” the Rev. Al Sharpton demanded on Monday, “I want my ticker tape parade.”

The civil rights activist and MSNBC host was referring, facetiously, to TheSmokingGun.com’s meticulously detailed, epic account, rife with court documents and law enforcement sourcing, of Sharpton’s apparent four-year career in the 1980s as one of the FBI’s more valuable mafia informants—a narrative that can best be described as The Sopranos meets American Hustle.

It’s a colorful chronicle that features con men and homicidal hoodlums with nicknames—as the Smoking Gun points out—such as “Benny Eggs,” “Chin,” “Fritzy,” “Corky,” and “Baldy Dom.” Also in the mix are famous performers like James Brown, the young Sharpton’s mentor and benefactor; Michael Jackson, Sammy Davis Jr., and rascally boxing promoter Don King, another associate of the fledgling Baptist minister.

The latest inconvenient revelation is another chapter of Sharpton’s checkered past coming back to haunt him—or maybe just throwing into sharp relief his amazing rise from rabble-rousing street preacher to member of the Democratic Party establishment as well as anchor of his own weeknight MSNBC program, PoliticsNation. MSNBC had no response to the Smoking Gun’s story. Yet a screaming headline on the Drudge Report—SHARPTON WAS FBI MOB RAT—was hardly an auspicious way to begin a momentous week.

On Friday, President Obama—who has hosted Sharpton repeatedly at the White House, including at a recent dinner for the president of France—is scheduled to address the civil rights entrepreneur’s National Action Network convention at Manhattan’s Times Square Sheraton, where Education Secretary Arne Duncan and New York Mayor Bill de Blasio, among other political and media luminaries, are also expected to kiss the ring during the 4-day confab.

In an interview with The Daily Beast, Sharpton called the Smoking Gun’s story—versions of which have been circulating in the media for the past 26 years—“embellished,” “a stretch,” and “crazy.” He denied that he ever knowingly snitched on wiseguys for the FBI.

But William Bastone, the Smoking Gun’s founder and the story’s author, insisted: “If he didn’t think he was an informant, the ‘Genovese squad’ of the FBI and NYPD officials sure knew him to be an informant. He was paid to be an informant, he carried a briefcase with a recording device in it, and he made surreptitious tape recordings of a Gambino crime family member 10 separate times as an informant. He did it at the direction of the FBI, he was prepped by the FBI, was handed the briefcase by the FBI and was debriefed after the meetings. That’s an informant.”

Bastone reported that Sharpton secretly taped Gambino family member Joseph Buonanno, who went by “Joe Bana,” in ten face-to-face meetings as the mobster gossiped about blackmail, mob executions, shylocking and other criminal activities under the leadership of Vincent “Chin” Gigante. Sharpton, by most accounts a skilled interlocutor who knew how to “play dumb” and draw out his conversation partners, received small payments from his FBI handlers— “walking around money,” Bastone wrote.

He cites several other instances in which Sharpton’s recordings and other tips, based on his business and social contacts with members of four of New York’s five major crime families, led to wiretaps and convictions of key mobsters. One of them, Genovese soldier Federico “Fritzy” Giovanelli, was sentenced to 20 years behind bars for racketeering, in large measure because of court-approved wiretaps obtained with the help of Sharpton’s information.

Giovanelli, now 82 and three years out of prison, was in a joking mood when Bastone asked his reaction to the television’s host’s hidden role in his prosecution: “Poor Sharpton, he cleaned up his life and you want to ruin him,” Fritzy chided Bastone with a laugh.

Indeed, at 59, Sharpton has proved himself a miracle-worker in the art of reinvention—or, as he put it on Monday, “I’ve been able to make the transition, but I did it on my own.” He has, for one thing, shed half his 300-pound body weight since his troublemaking days as an angry outsider and exchanged those slovenly tracksuits for elegantly tailored duds. Hardly anyone, certainly no polite person, ever mentions the Tawana Brawley hoax anymore.

On Monday, however, Sharpton found himself doing energetic damage control regarding the Smoking Gun’s story. In interviews, he portrayed himself as a concerned citizen who, as a self-described “civil rights kid” of 29, reached out to the Feds after his life was threatened by mobsters, in order to expose a criminal conspiracy in the music business to cheat African American performers and promoters out of fair compensation.

He did so, he argued, at the risk of life and limb—and certainly there’s little doubt what might have happened to him if his gangster contacts thought he was dropping a dime on them. Even Bastone seemed to acknowledge that with some of the targeted mob figures alive and kicking, simple prudence might make Sharpton believe he should continue to deny a secret arrangement with the FBI and stick to the cover story he included in his 1996 autobiography, Go and Tell Pharaoh, and last year’s best-seller, The Rejected Stone.

“Yes, you’d want to keep that on the QT,” Bastone said. “But time has moved on from when he did it. Perhaps the danger has subsided.” Still, Barone said such concerns don’t justify Sharpton’s “going out of his way to deny it.”

“I think they take a lot of leaps here,” Sharpton said about the Smoking Gun, which asserted that the young activist was “flipped” by the FBI and coerced into being an informant after blundering into a sting operation in which an undercover agent, pretending to be a drug lord, got him on videotape apparently countenancing the idea of taking a 10 percent cut for helping in the importation of “pure coke” at $35,000 a kilo.

But the Smoking Gun concedes that a successful prosecution would have been iffy, at best, based on the video, in which Sharpton merely nodded, said “I hear you,” and speculated on the market needs of an unnamed buyer: “If he’s gonna do it, he’ll do it much more than that.” For years Sharpton has claimed that far from being intimidated by the FBI into becoming an informant, he dared the agents, “Indict me.” That never happened.

“The government was trying to entrap a civil rights kid on some crimes that were never committed, and failed to trap him,” Sharpton said on Monday. “That’s the unsaid part of it: Why did they go after Sharpton in the first place? What was the crime?” He added: “The one interesting thing that we’re looking at, three decades later, is that no one can identify, with all of the documents Bastone’s got, what it is they came after me for? There is no crime here.”