In considering the "fighting them there so they won't come here" argument, Matthew Yglesias points out the obvious conflict between symbolism (retreating from Iraq makes us look weak) and reality (staying in Iraq causes us to actually be weak). He seems perplexed by the Right's tendency to "view national security policy as something that takes place entirely at the level of symbolism". This is, I think, not so difficult to understand. American conservatives live in an alternate reality, unable to distinguish between symbolism and reality. To them, symbolism is reality. If you listened to enough conservative radio and watched enough Fox News you'd live in that alternate reality too. Never was this more clearly illustrated than in Ron Suskind's famous discussion with an undisclosed White House official (Andrew Card, perhaps?) about how the Bush administration was in a constant process of creating its own reality. This was never a matter of the Bush administration being able to fundamentally alter the state of the world directly through their pronouncements and news releases, but rather an expression of the belief that if they can control news cycles and assert a concept of reality strenuously enough, everyone else would have little choice but to accept it as real, and the world would adjust itself to the White House's vision. It was Wag the Dog transformed from satire into official state policy. They could reshape reality through symbolism by convincing people that what they thought was true actually wasn't.
Obviously this doesn't work. There are too many competing sources of news and reality does eventually trickle in to displace this fictional presentation. The reality-based community inevitably gets the last laugh, as Suskind pointed out. This is why the administration and their supporters were always so furious about the media reporting on bloodshed in Iraq and missing the "good stories"; the media was deconstructing the administration's carefully constructed alternate reality.
But it's not hard to see why conservatives got suckered into this belief, and why they still can't seem to let go of it. Most conservative news sources are mere propaganda outlets. Witness the old Pew study finding that the more people watched Fox News the more likely they were to believe that we had found WMD's in Iraq or that Saddam was behind 9/11. Or this more recent Pew study that shows that while liberals see Republican presidential candidates in exactly the same way conservatives themselves view them, conservatives, by contrast, see all of the Democratic candidates as raving left-wing lunatics. American conservatives have replaced their own reality with symbolism, so why wouldn't it be natural for them to think the same is true for everyone else? Their own echo-chamber media has relegated them to a world that only exists in their own minds.