Whose sarin?

"The complaints focus on what Washington did not have: any advance warning from the assumed source of the attack."
Absence of evidence is not evidence of absence. This was true when Bush and Blair told us the lack of weapons of mass destruction in Iraq meant they must have been hidden. Now it can be applied to Seymour Hersh's genocide denial.
Hersh bases his case on a couple of further propositions. That the al-Nusra front is a suspect in previous attacks. There is no evidence for this, except for some guy called Tariq who knows how to make mustard gas having been seen in Damascus. That the munitions could as easily have been fired by opposition forces. Apart from the improbability of any rebel forces hiding this from the population that are fighting on behalf of, the technical details are dealt with by the Brown Moses Blog*.
"An unforeseen reaction came in the form of complaints from the Free Syrian Army’s leadership and others about the lack of warning." So if there was some plot [sic], the FSA weren't in on it. 'Unforeseen' seems to mean, 'doesn't fit Hersh's narrative. He then implies that the figures for the dead are all over the place, deprecating 'The strikingly precise US total'. This is an administration that he's claiming knows every time a jar of chemicals moves in Syria, but can't work out how many people are killed in a documented attack? No.
"The Obama administration, committed to the end of the Assad regime and continued support for the rebels," is contradicted by, "Obama turned quickly to the UN and the Russian proposal for dismantling the Syrian chemical warfare complex."
*[http://brown-moses.blogspot.co.uk/…/new-key-evidence-in-und…]