The focus of commentary and argument since the shooting in Tuscon on Saturday is whether the violent rhetoric of the right-wing media and politicians is to blame. The right wing argues that the man who did it was mentally ill and that it had nothing to do with ideology. That, of course, begs the question whether or not the mentally ill might be especially susceptible to the hate mongering even if they themselves have no special investment in the politics or ideologies. But that misses the phenomenon that is really at the center of these killings or attempted murders of politicians and others involved in politics.
Over the hump ....
Instead of looking at the motivations of the killers or attackers, look instead at the victims or intended victims of their violence. One thing stands out, at least to me: most are Democrats or progressives/liberals.
From Wikipedia and here one can see this clearly since post-WW II, starting with Truman. Things clearly pick up in the 60s with the Kennedy's, MLK and others. Just from these sources, I count 8 Democrats/progressives/liberals versus 4 Republicans and conservatives, including Presidents Nixon, Reagan, Ford and the Nazi George Lincoln Rockwell. I didn't count Judge Roll since even though he was appointed by H.W. Bush he seemed to have progressive leanings (which led to his needing police protection at one point). I didn't count John Lennon and Malcom X mentioned in the second source. I also didn't count the innumerable civil rights workers or pro-choice doctors and activists. If I had, it would be a much larger disparity between the left and right.
So the question is not whether right-wing rhetoric and hate mongering is responsible for assassinations or attempted assassinations, but rather why do Democrats and progressives tend tend to be the victims of such violence. Perhaps, more specifically, the question of the role of hate speech should not be focused on the perpetrators, but on the victims. In other words, one might ask whether hateful right-wing rhetoric incites violence against Democrats and progressives independent of who commits it.