Paul Krugman thinks that there is a wave of "extremism" and "hate" being fed by the media and political establishment. If there is, he ought to know. He's doing the serving.
There are three moves here. The first is to pick convenient lunatics who have committed a violent act and whose inner demons express themselves, if loosely, in political terms. The nutters of the hour are Scott Roeder, who shot abortionist George Tiller, and James von Brunn who opened fire at the Holocaust Museum. You ignore inconvenient tilted heads like Carlos Bledsoe (a/k/a Abdul Hakim Mujahid Muhammad) who killed a military recruiter in Little Rock.
Next, you characterize these jumblebrains as "members of" or "associated" with the right as if fevered minds harbored linear thought. This move may be difficult because - at the extremes - left and right often meet. von Brunn, for example, could just as readily be called a member of the extreme left as of the extreme right. Ignore what doesn't fit.
And that brings you to the final move: the blurring of distinctions between the sane and the short circuited. The way to do this is to cherry pick either ill considered statements (Glenn Beck reported internet rumours of FEMA concentration camps before he debunked them) or harsh words (like calling someone who aborts babies that are about to be born a "killer"). You must then claim that whoever has said these oh so awful things is the "face of" conservatism. The leaders of the Republican Party cannot be Sarah Palin, Michael Steele, or Bobby Jindal. They must be entertainers like Rush Limbaugh or Michelle Malkin.
You must, at all costs, avoid any mention of Howard Dean, Keith Olberman, Al Gore, Al Franken, or Joe Biden. (These are, after all, marginal figures on the left.) It is critical to ignore stupid claims (Bush knew 9-11 was coming) and intemperate language (Bush is an evil war criminal) that do not fit the narrative.
You then abandon critical thought. Shooting abortion doctors is a small step from speaking harshly of abortion even if strident attacks on the mission of America's military or wild claims about the "death" of the planet do not - and could not - lead to violence. There is no real difference between Wisconsin Right to Life and Operation Rescue. Opposition to affirmative action is sort of like white supremacy. Imply, if you can, that tonight's broadcast of Hannity and a few Jager shots are all that separates Timothy McVeigh from Bill Kristol.
Suddenly, your political opponents become terrorists. Neat trick if you can pull it off.