The deniers employ this tactic of anomalies-as-proof to great effect. David Irving, for example, claims that there are no holes in the roof of the gas chamber at Krema 2 at Auschwitz-Birkenau. So what? So plenty, he says. No holes in the roof of the gas chamber at Krema 2 means that the eyewitness account of SS guards climbing up on the roof and pouring Zyklon-B gas pellets through the holes and into the gas chamber below where the prisoners were herded into, means that the eyewitness account is wrong, which means that no one was gassed in Krema 2, which means that no one was gassed at Auschwitz-Birkenau, which means that no one was gassed at any prison camp, which means that no Jews anywhere were systematically exterminated by the Nazis. In short, "no holes, no Holocaust," says David Irving, a slogan emblazoned on t-shirt of his supporters at his London trial in which he sued a historian for calling him a Holocaust denier.
No holes, no Holocaust. No melted steel, no Al-Qaeda attack. The parallels are equal, and equally flawed.