With regards to Iraq's no existing WMDs, which were used to launch a war on it, the Bush administration's sell-points were not so much single pieces of (false) evidence, the Uranium from Nigeria, the bio-weapon trucks, the Antrax scare, but the sum of all of these pieces.
Even people who did not believe every single piece of the evidence could be convinced by pointing to the sum of them. A lot of dirt was thrown at Saddam's Iraq and for a lot of onlookers the amount of dirt thrown, even as it didn't stick, was enough to make Iraq look dirty.
In responses to the new Sy Hersh piece on the non-existence, which U.S. intelligence agencies confirm, of an Iranian military nuclear program, the Obama administration is now using exactly the same tactics. It asserts that the validity of each single piece of evidence is not relevant, it is simply the sum of them is what makes Iran dangerous.
In a Politico piece the administration responds directly to the Hersh piece:
“There is a clear, ongoing pattern of deception, and Iran has repeatedly refused to respond to the IAEA’s questions about the military dimensions of [its] nuclear program, including those about the covert site at Qom,” the senior administration official added. “These examples and more make us deeply skeptical of Iran’s nuclear intentions.”
The communicated strategy here is: "It is the sum of the evidence (about some of which we will not tell you), not the single explainable pieces, which makes Iran guilty."
It therefore does not matter to the "senior administration official" that the Qom sides was not secret at all. Iran declared the then still empty site to the IAEA on September 21 2009 and the Obama administration revealed it as "secret" only on September 25 2009. But that false evidence is only part of a pattern of other (likely also false) evidence and that is the reason, says Obama, why we must eventually bomb Iran.
In the New York Times the propagandist Broad lets the administration make the same point:
The seven categories of technology all bear on what can be interpreted as warhead design: how to turn uranium into bomb fuel, make conventional explosives that can trigger a nuclear blast, generate neutrons to spur a chain reaction and design nose cones for missiles.
Two diplomats familiar with the evidence, both of whom spoke on the condition of anonymity under the usual protocol, emphasized that no single one of the technologies stood out as indicating bomb work. Some, they conceded, have peaceful uses.
But the totality of the evidence, they said, suggested that Iran has worked hard on multiple fronts to advance the design of nuclear arms.
“It’s the whole variety of information,” one of the diplomats said. “You have to look at the whole thing.”
(Notice how Broad hides his sources as "diplomats" not as "foreign diplomats" as the NYT usual does when they are not U.S. administration officials.)
But despite of what those administration stooges say, the "totality of the evidence" is not greater than zero when each and ever evidence point is zero. Any of the "seven categories of technology" has peaceful or non nuclear military purposes. Some of them are even very unlikely to be used in a military nuclear program.
A few weeks ago a scare was made of evidence of uranium deuterite as neutron generator in an Iranian bomb. As the Arms Control Wonk Jeffery Lewis pointed out:
This method is incredibly unique. Not only are there no civilian uses for imploding uranium deuteride to generate a burst of neutrons, NOT EVEN THE OTHER NUCLEAR WEAPONS PROGRAMS CONSIDERED THIS APPROACH.
Why, if Iran would build a bomb, would it use an unproven technology no one else has ever used for this purpose? Would you introduce some obscure new physics into your very first bomb if all the other experienced bomb builders used other better and by now well known, readily available and reliable methods? That is again not credible as evidence. But to the Obama administration that does not matter.
There new selling point is not the credibility of their alleged evidence, they even confirm that there is none, their selling point is the pattern THEY create by introducing all kinds of dubious technical evidence to make their case.