The important thing here is not to blame conservatives or anti-Muslim types - it's to recognize that those groups, and many people here, have been all too quick and happy to play the blame game when it suits their politics. It's wrong to do it to Muslims, wrong to do it to leftists, and just as wrong to do it to "right wingers."
There is something to said about toning down the "x group declared war and wants to enslave you!" rhetoric. When Muslims engaged in constant demonization of America for political reasons, the result was that mentally unstable extremists hopped on board and decided to "defend" against their demonic enemies through terrorism.
Now precisely the same thing is happening to right wing, anti-immigrant, anti-leftist movements. They've spent all the past decade claiming that anyone with a leftist economic policy or a tolerant view of Islam is conspiring to destroy the western world. Now theyre blogging shocked, shocked that someone actually believed their claims about the Muslim/leftist plots enough to consider violence in response.