It is puzzling that so little has been made of Seymour Hersh's latest story. Now 77, 'Sy' Hersh's name first resonated in 1969 when he exposed the massacre at My Lai, in which US infantrymen machine-gunned between 347 and 504 Vietnamese civilians, most of them women and children.
Some babies were bayoneted, some women raped and mutilated in unspeakable ways before being dumped in a ditch. Even at this distance in time, pictures of the scene are too horrifying to view for more than a moment.
The horror would have been worse if three US servicemen had not come upon the killing in a helicopter, landed and placed themselves between the soldiers and the huddle of surviving villagers, guns pointed at their fellow GIs.
The soldiers who intervened were denounced as traitors by members of Congress, including the chair of the armed services committee. Hersh became a target for hate and threats of death.
Thirty-six years later the same element railed against Hersh again when he revealed how Iraqi detainees in Abu Ghraib prison in Baghdad were being tortured.
In both cases some of Hersh's critics genuinely couldn't believe that Americans were capable of such barbarous behaviour. Others appeared simply to shrug that the victims by definition were enemies of the US and therefore fair game.
It may be that many are finding it difficult now to credit that the gas attack on civilians in the Damascus suburb of Ghouta on August 21 last year was perpetrated not by the Syrian regime, but by America's allies against the regime.
In a report in the London Review of Books, Hersh suggests that the attack was a "false flag" operation by anti-Assad rebels acting in collusion with elements of the Government of Turkey – a member of Nato.
In 2012 Obama had declared that any use by Assad of chemical weapons would cross a "red line" and trigger US retaliation. Initial reports of the Ghouta attack assumed Assad's guilt.
In response Obama ordered the military to prepare not a punishing strike, but an all-out bombardment: "The core targets included electric power grids, oil and gas depots, all known logistic and weapons depots, all known command and control facilities and all known military and intelligence buildings."
But two days ahead of this planned onslaught Obama hesitated and announced he would seek Congressional approval before going ahead. A few days later he backed off further, accepting a Russian-brokered agreement whereby the US cancelled the operation and Assad agreed to give up his chemical arsenal. What prompted Obama's U-turn?
Hersh says that, shortly after August 21, Russian military intelligence obtained samples of the sarin gas used in the Ghouta attack. They analysed it and passed it on to their British counterparts. The chemical warfare research centre at Porton Down confirmed the Russian view that the gas matched none of the strains which the agencies knew Assad was holding.
The British officials, Hersh says, sent the Americans a message: "We're being set up here." This stiffened suspicions already troubling US military chiefs about Obama's apparent eagerness for major military action. "There was no way they thought Syria would use nerve gas at that stage, because Assad was winning the war."
The joint chiefs of staff, the narrative continues, told Obama that his ground for going to war wouldn't stand up, the attack would be seen as "an unjustified act of aggression". It was at this point that Obama announced he would be consulting Congress and that the Russian-sponsored deal with Damascus came into play.
"Nobody wants to talk about all this," Hersh quotes a former US intelligence official. "There has not been one single piece of additional evidence of Syrian involvement in the sarin attack since the bombing raid was called off... And, since we blamed Assad, we can't go back and blame (Recep) Erdogan."
The story depicts Obama not as a moderate, liberal President restraining right-wing enthusiasts for war, but as a man eager to be seen as a tough-minded commander-in-chief having to be restrained by the military from irresponsible adventurism.
The story brings into focus, too, the fact that the Ankara regime of Recep Erdogan is allied with one of the fiercest of the jihadist factions of the splintered anti-Assad movement, the al-Nasra Front, also associated with al-Qaida.
All we can say for certain about the implications of this cat's cradle of murder, conspiracy and lies is that they are terrifying. Which, perhaps, is why, again, so many are averting their eyes from a Sy Hersh story.