Of all the Palin-haters on the internet, there's probably no one with a higher profile than Andrew Sullivan. I doubt there is anyone who has done more to demonize Palin. Oh there are plenty of people who spew hatred of Palin, but Sullivan does it from a heavily-trafficked blog at The Atlantic. And unlike most of those on the left, who are easily recognizable as fringe loons, Sullivan is not only highly prolific, but an excellent writer who comments on all sorts of subjects. On the rare occasion he even offers a reasonable analysis. Casual readers not familiar with him and his obsession with Sarah Palin might be inclined to take him seriously.
Let's suppose someone shows up at a Sarah Palin speech and shoots her along with various bystanders. The shooter is clearly disturbed, has no clear political ideology, and harbors a grudge against Palin. There's no evidence he's ever read anything by Andrew Sullivan, and to all appearances he acted based on his own unbalanced mental condition. Would it be reasonable to blame Andrew Sullivan for the shooting, or even to suggest that he's created the climate that made such a shooting likely? Should we comb through his writings to see if he ever used any sort of violent imagery in any way, no matter how routine or innocuous, with reference to Palin? Despite the fact that Sullivan has never advocated violence against Palin, would he still bear some responsibility for the shooting? In my opinion the answer is no, and that answer should be blatantly obvious. I'm sure Sullivan himself would be appalled at the notion that he might bear some blame for the actions of a deranged individual. But of course, like the intellectually dishonest, logically-challenged individual that he is, he has no problem trying to tie Palin to the Arizona incident despite the fact that she had nothing to do with it.
It shouldn't even need to be pointed out, but there is absolutely no evidence at all that the current state of political discourse, the political climate, or whatever else people are calling it had anything at all to do with this shooting. No one knows for sure what drives this type of killer to commit his actions. But people don't like to admit that they just have no idea what causes such shootings. They prefer to look for something or someone to blame. And who better to blame than political opponents?