The shooter lists the Communist Manifesto among his favorite books. This is hardly Palin and Beck teritory. Among the killed was one of the most conservative judges in Arizona.
Crazy Schizophrenics do Crazy things. Its what they do. Its because they are crazy.
The actions of those who leap on every thing a crazy schizophrenic does to try to turn it to partisan advantage, though, are harder to justify. The best that could be said for some of them, is a tendency to overwhelming confirmation bias. Of course, those who are revealing their bias that all who disagree with them are crazy, should contemplate themselves, perhaps.