What mythago said.
I sense that we're going to be overwhelmed with attempts to distance Loughner from the right wing world. "Somebody who knew him in high school says he's a liberal (not that it matters)" kind of stuff. We'll probably also hear "He was crazy, so the fact that politicians and commentators use the rhetoric of violence may not have actually made this shooting more likely." But that misses the larger point, which is that the rhetoric of the likes of Palin, Beck and Coulter legitimizes a mindset that is inherently anti-democratic (small "d" - in a democracy we solve our political disputes at the ballot box, not with guns) and whatever the intention will inevitably be taken literally by some percentage of the population.
It's not acceptable to shrug, "They're speaking metaphorically, so it doesn't count." They only back away from their statements when a price is imposed - and a price is rarely imposed and is even less likely to be significant. "Oh, the crosshairs on targeted Members of Congress were 'crosshairs that you would see on a map'? [Added: the latest 'explanation'.] I don't think I've ever seen that, and it doesn't explain the associated slogan, 'Don't Retreat, Instead - RELOAD!', but... good enough for us."
The more common result appears to be reward - the violent rhetoric or imagery is covered by the media but not criticized (or criticisms are reported from political opponents while the news show depicts the exchange as routine politics), the speaker continues to get "talking head" spots on mainstream media shows... or gets hired to host shows... the sky's the limit. Let's recognize this for what it is in the hands of people like Beck, Palin and Angle: the deliberate use of a known political formula that brings fame, money and political influence.
The political views of Loughner are irrelevant to this issue, as are the political views of the likes of Palin and Beck. Their conduct is the problem, not their political beliefs. If there were a left-wing radio firebrand using equivalent rhetoric, he too would be part of the problem. If he were embraced by the Democratic Party, were an opinion leader for that party, or were considered to be a serious contender for its next presidential nominee, that would highlight a serious problem within the Democratic Party. It's well past time for the mainstream media and the Republican Party to stop embracing the crazy, but if they choose to continue do so they should do as mythago suggests - take credit for legitimizing violence in the political arena and for its bloody consequences.