I get what Dean means! He is saying that since America has not suffered any more 9/11-like attacks since 9/11, the capture of Saddam could not have possibly made America any more safe than it already was. Perfection is hard to beat, he notes. It follows that no action whatsoever can make America "safer", in the world-according-to-Dean, but only either "as safe" or "not as safe". As Dean did not say America was "not as safe" as it was before Saddam's capture, he must mean that the capture made America "as safe" as it was before, that is, its effectiveness was 100%. Being "conservative", it took me a while to understand Dean's straightforward language.