Folks, "the rhetoric" really just ain't that bad. On either side.
The fringe right and left are "fringe" for a reason - most people don't buy that trash. In general, things are pretty ordinary in terms of political discourse. If we really are going to get all worked-up about the use of very common and well-worn cliches that borrow the terminology of beatdowns and barroom brawls, I think we're badly in need of what Mark Shea calls "Insensitivity Training".
The Arizona shooter, Loughner, was a grenade with the pin pulled, and it appears to me he would have acted out sooner or later regardless of who was president, whether his state rep had a "D" or an "R" after his/her name, or whether Sarah Palin had little crosshairs on her frakkin' web page or not.
He is a NUT. Everyone is looking for a logical and comprehensible series of events that led up to this - because we find logical explanations comforting - but it cannot be found. It makes no sense. It was not logical or comprehensible. He had an insane worldview. Whether this was because he was insane first, or whether his philosophy drove him mad may be up for debate, but in terms of his place in society, he is just not even on the map... right or left.