Read the whole thing:
Glenn Reynolds: The Arizona Tragedy and the Politics of Blood Libel - WSJ.com: "Shortly after November's electoral defeat for the Democrats, pollster Mark Penn appeared on Chris Matthews's TV show and remarked that what President Obama needed to reconnect with the American people was another Oklahoma City bombing. To judge from the reaction to Saturday's tragic shootings in Arizona, many on the left (and in the press) agree, and for a while hoped that Jared Lee Loughner's killing spree might fill the bill.
With only the barest outline of events available, pundits and reporters seemed to agree that the massacre had to be the fault of the tea party movement in general, and of Sarah Palin in particular. Why? Because they had created, in New York Times columnist Paul Krugman's words, a 'climate of hate.'"