George Will writes in the Washington Post:

It would be merciful if, when tragedies such as Tucson's occur, there were a moratorium on sociology. But respites from half-baked explanations, often serving political opportunism, are impossible because of a timeless human craving and a characteristic of many modern minds. The craving is for banishing randomness and the inexplicable from human experience. Time was, the gods were useful. What is thunder? The gods are angry. Polytheism was explanatory. People postulated causations. And still do. Hence: The Tucson shooter was (pick your verb) provoked, triggered, unhinged by today's (pick your noun) rhetoric, vitriol, extremism, "climate of hate." Demystification of the world opened the way for real science, including the social sciences. And for a modern characteristic. And for charlatans…. This McCarthyism of the left - devoid of intellectual content, unsupported by data - is a mental tic, not an idea but a tactic for avoiding engagement with ideas. It expresses limitless contempt for the American people, who have reciprocated by reducing liberalism to its current characteristics of electoral weakness and bad sociology.

This morning on C-SPAN, Bill Kristol also labeled the reaction from the left to the horrific shooting in Tucson as a form of McCarthyism:

A conservative pundit on Monday ripped liberals who have suggested that Sarah Palin is to blame for the shooting tragedy in Arizona. During an appearance on C-SPAN's "Washington Journal," Bill Kristol of the conservative-leaning Weekly Standard magazine called the criticism of the former Alaska governor "a disgrace."   He said there is no proof that Jared Loughner, the suspect, was a fan of Palin or went to her website, which had labeled Rep. Gabrielle Giffords (D-Ariz.) and other Democrats a political target last year; it was illustrated with a graphic of crosshairs that has triggered a political debate…. Kristol said those who are blaming Palin, such as Paul Krugman of The New York Times, are practicing "McCarthyism." "The attempt to exploit this tragedy is distasteful," Kristol said.  He added that both parties have used words like "targets" in seeking to win political campaigns. And Loughner doesn't appear to have been involved in partisan politics, he said.