From his latest column:

The Nazi comparisons from Rush Limbaugh; broadcaster Mark Levin asserting that President Obama is “literally at war with the American people”; former vice presidential candidate Sarah Palin claiming that the president was planning “death panels” to extirpate the aged and disabled; the charges that the president is a fascist, a socialist, a Marxist, an illegitimate Kenyan fraud, that he “harbors a deep resentment of America,” that he feels a “deep-seated hatred of white people,” that his government is preparing concentration camps, that it is operating snitch lines, that it is planning to wipe away American liberties": All this hysterical and provocative talk invites, incites, and prepares a prefabricated justification for violence...

It's not enough for conservatives to repudiate violence, as some are belatedly beginning to do. We have to tone down the militant and accusatory rhetoric.