It seems like newspapers are, in the wake of the horrible shooting at Rep. Giffords' event, waging an ongoing debate over ``civility'' in public speech, directly and indirectly the question of whether the event was the result of increasing hostile, enemy-of-the-state type political speech (which, often and especially from conservatives, invokes the use of military or firearm metaphors, to little real informational benefit), or the result of a killer who, tragically, had become a completely unhinged mess to whose actions causality can't easily be ascribed. I lean towards the second view. It's not that I particularly like the kind of political speech that goes around -- I'd like to hear more real content -- but I think its effect here is at best marginal. I understand I might be wrong on that though. The problem is that the case for the influence of political speech is made by two types of person: those with a genuine concern for the downstream consequences of violence-referencing political speech, and those seeking political advantage (and I believe that most speakers in public now are so much tools of political ``teams'' that basically they'll echo the political advantage line unconsciously).
It seems to me that if one seriously wanted to make the causality argument, though, one is obliged to address the overall presence of violence in our culture. People have been complaining for decades, I think rightly, about the amazing amounts of consequence-free, casual violence and carelessness for human dignity in film, on television, and in popular music. Lately of course computer games -- with which I have little familiarity -- have become omnipresent and actual grownups can talk in public about playing them often, and these things are amazingly graphic and violent and put the man-child user in the position of casually killing.
Our society is ever more steeped in violent images and language, in which now the most blah suburbanite can participate. In that context political speech presumably has to get ever more extreme to even register. So I don't have any real faith in a ``political speech alone'' understanding of what happened, and I'd assume any good-faith (as opposed to opportunistic) attempt to talk about what happened as something prompted by outside speech, could at best talk about political speech as a directing influence for an already-combustible individual, or as a last straw over a mountain of violent images. I think an honest approach would have to at least nod to the vast increase of violent imagery in the culture.
Among many many pieces attributing the murders to political speech, I have not seen that nod even once, and I am therefore inclined to write them all off as conscious or unconscious opportunism.