Gregg Schwarz frowned as he positioned himself, just so, in front of the wrought iron fence surrounding John Edgar Hoover’s grave, a place he has visited countless times but never before in anger.

A retired FBI agent who joined the agency in 1972, the year Hoover died, Schwarz had hired a videographer to film him for YouTube expressing his displeasure with a movie that depicted Hoover as a repressed homosexual. In a dig at Clint Eastwood, the director of “J. Edgar,” Schwarz titled his video response, “Dirty Harry to Filthy Harry.”

“Mr. Hoover was portrayed as an individual who had homosexual tendencies and was a tyrannical monster,” Schwarz said into the camera, as the sun glinted off his FBI cuff links and FBI lapel pin. “That is simply not true.”

Many former FBI agents share Schwartz’s pique with the film’s dropped hints of an abiding love between Hoover and aide Clyde Tolson, who is buried a few grave sites away. Historians agree that there is no evidence that either man was gay, and a request for comment from either Eastwood or screenwriter Dustin Lance Black was declined.

Since “J. Edgar’s” release early this month, hundreds of agents have griped about the film on xgboys, a closed e-mail list for FBI retirees that takes its name from one of Hoover’s pet dogs, which in turn is a play on the old nickname for federal agents, “G-men.”

“I don’t know anyone who’s not extremely upset,” said Bill Branon, a former agent who is chairman of the J. Edgar Hoover Foundation, which grants scholarships to college students studying law enforcement and forensics. “It’s not only because of our admiration for him. It’s the fact it’s just not true. If it were true, it wouldn’t be the worst thing in the world. But don’t do that to the poor guy when he’s dead and gone.”

The widespread unhappiness over Hollywood’s imagined rendering of Hoover’s rumored-but-never-proven personal life largely comes from men who started their FBI careers when Hoover was still in charge. Their devotion is undimmed almost four decades after his death.

Nowhere is that more evident than at Hoover’s grave at Congressional Cemetery. The headstone usually has several stones perched atop it, a sign of recent visitors. There are often fresh flowers inside the wrought iron fence that was forged by a former agent turned metalworker. Retired agents periodically tend to the grave site, removing weeds and overgrown grass. And some newly minted agents make post-graduation pilgrimages there, even though Hoover is not on the curriculum at the FBI Academy.

Agents younger than 70 or so don’t get it, said Brad Benson, president of the Society of Former Special Agents of the FBI.

“Devotion is probably a good word for my generation and up,” said Benson, 70. “The more recent people can’t understand why all the energy is being devoted to this when our [retirement] benefits are at stake.”

Older agents say their admiration for the late director is cemented in his role in building up the FBI and instituting several law enforcement innovations, such as crime labs and fingerprinting databases. Many cite his thoughtful gestures, the kind that engender loyalty, including the personal notes he sent to mark special occasions in an agent’s family — such as births, deaths and anniversaries.

But mostly, they say, they are offended on his behalf because the intimation that Hoover was gay is false. They say agents, apparently a gossipy bunch among themselves, would have heard about it if it were, because Hoover was always tailed for his protection, despite his objections; they called it “Hoo-Watch.”

“It’s hard to have an illicit homosexual love affair with an agent looking in the back window of your car,” said Fred Robinette, a former FBI agent and Hoover’s grand-nephew.

John Fox, the FBI historian, said speculation about Hoover’s sexuality never got very far. “Hoover was single all those years,” Fox said. “His closest friend and associate was another man. Periodically through the history of his tenure, there was an innuendo here, an innuendo there that he was homosexual. But that was the extent of it.”

What is known is that gay men were blackballed from the FBI during that era because Hoover considered them vulnerable to blackmail if their sexual orientation were discovered.

“He thought people with homosexual tendencies were a security risk,” Schwarz said. “Everybody knew it at the time. Anybody who thought homosexuality was a security risk would not, and did not, condone that type of activity.”

Former agents who were consulted said they told the filmmakers that rumors of Hoover’s homosexuality were untrue.

Cartha “Deke” DeLoach, a former high-ranking FBI official whose office was across the hall from Hoover, said he told that to both Eastwood, who called him for advice, and Leonardo DiCaprio, the actor who played Hoover. In a sit-down meeting with DeLoach, DiCaprio asked DeLoach to help “make me Hoover.”

“He said he didn’t think the movie was going to delve into it in great length,” DeLoach said of DiCaprio. DeLoach praised both Eastwood and DiCaprio as decent men but added, “It’s wrong making insinuations [Hoover] was homosexual. I think it was an attempt to gain popularity, and they had to use several insinuations that weren’t correct.”

When Branon, of the J. Edgar Hoover Foundation, started hearing rumors the film would portray a sexual relationship between Hoover and Tolson, he wrote Eastwood a letter seeking reassurances.

“It would be a grave injustice and a monumental distortion to proceed with such a depiction based on a completely unfounded and spurious assertion,” said the letter, dated April 8 and posted on the foundation’s Web site along with Eastwood’s response.

In an April 13 letter, Eastwood wrote: “Please rest assured that we do not give any credence to cross-dressing allegations . . . nor do we intend to portray an open homosexual relationship between Mr. Hoover and Clyde Tolson,” the letter says.

Some agents say their confidence was misplaced.

“We were led to believe this would be an accurate portrayal of Mr. Hoover,” said Thomas McGorray, who runs the e-mail list xgboys. “Everybody feels betrayed. It’s typical Hollywood. They went off on the sex stuff.”

As a technical adviser on the film, former agent Scott Nelson said he also advised the filmmakers it was “gratuitous” to include a scene showing Hoover and Tolson kissing and to show Hoover putting on his mother’s dress in his grief after she died.

But Nelson thinks some of his fellow former agents are overreacting.

“It’s a biopic. It’s not a biography,” said Nelson, who now runs his own security firm in California. “That doesn’t mean it’s factual. Agents deal in fact, and they’re offended at the literary license taken by the screenwriter. I know why they’re offended.”

However, Nelson said, the film does not disparage Hoover, and the speculative focus on his personal life was part of dramatic storytelling: “That’s Hollywood.”