The fact that Kennedy’s assassin was an unstable, poorly educated radical Communist who had spent time in Russia and thought he had a grudge against the US was barely reported even at the time. I lived through this, and as soon as the press realized that Oswald’s connections were entirely left-wing (in fact, extreme left), analyses of his motives disappeared from view...and then he was dead.
I think this current assassin, Loughner, was probably unstable at best and psychotic at worst. The latter may have been the result of some adult-onset form of schizophrenia, or it may possibly have been caused by excessive dope smoking. In high school in the 60s, I knew stoners who smoked so much that they were afraid to go into their lockers because “they” were watching them. I was never sure who “they” were, but then again, I didn’t dare ask.
More recently; Lefty mayor Bloomberg commented on the failed Times Square bomber as being someone unhappy with the healthcare debate.