As Josh Marshall says their behavior has been abhorrent,
Everything that's happened over the last five days has grown from a pattern of incitement going back almost a year -- wildly hyperbolic statements, coded appeals to menacing behavior, flippant jokes about bringing firearms to political events and all the rest.
The only quibble I have with Josh is that the pattern of incitement actually goes back to the fall of 2008 and the McCain/Palin campaign. Remember "pals around with terrorists?"
The modern GOP is borne out of Nixonian politics of resentment and not a coherent set of a conservative ethos. In order to keep this ragtag coalition together there must always be an Other to blame and a common sense of victimization stoked. Sustained rage is the magic elixir, it's the only thing that is holding the party's various factions together - rage at some Other.
The problem of course is that each time you whip the rubes into a frothy lather over some trumped up or fabricated controversy you have to go bigger, louder and more hyperbolic than the last time. The other issue is that while John Boehner, Eric Cantor and most (though certainly not all) of the rest of the GOP officials who are stoking this rage know that it's all just Kabuki Theater, but do the Tea Baggers and militiamen?
Perhaps something will snap in a prominent Republican sometime soon and that he or she will take a forceful public stand against the incitements. More likely though is that the Eric Cantor's of the world will continue to incite this rage until it finally boils over in a terribly violent incident. I'm just hoping that no one actually dies, I think the violent act itself is all but inevitable at this point. With immigration reform looming this summer I think the elements are all in place.
Finally, when it (whatever "it" is) occurs you can bet your bottom dollar that Republicans will be spinning to blame the act on liberals, the media, the President or someone else. Remember, the sense of perpetual victim-hood is central to the psychology of the movement - they won't drop that mask easily.