This post by Atrios captures the essential dynamic after 9/11 quite well. He has a lot to say, go read it, but one thing struck me from his first paragraph:
Obviously it was incredibly naive to think that this crew would, after 9/11, come anywhere close to doing the right thing. But what I certainly wasn't capable of predicting at the time was how a horrific event perpetuated by extremist religious fundamentalists could somehow be converted into a sustained attack on... liberals. What I didn't understand then was the basic conservative worldview that if it's good it's conservative and if it's bad it's liberal.the emphasized text being the part of note. It came as a surprise to a lot of folks, but it really should not have. This dualistic attitude is common throughout the conservative, especially the religious right community. It often shows up in the arguments made by creationists against evolution. Much of what the young earth creationists argue makes little sense except in terms of a view of the world in which all is either good or evil and there is no overlap. So God and religion and the bible and creationism are good, and anything opposed to these things, for example evolution, are evil. It should hardly be surprising that many would also see conservative as good and liberal as evil.