Editor’s Note: Each week we cross-post an excerpt from Katrina vanden Heuvel’s column at the WashingtonPost.com. Read all of Katrina’s column here.   A colleague invoked Robert Frost: "Poetry is about the grief. Politics is about the grievance." This is a time of grief, not grievance. The crazed act of a clearly unstable man in Arizona has taken six lives and wounded 14 people, with Rep. Gabrielle Giffords still fighting for survival.

This was an assassination of democracy, an armed assault on citizens gathered to exercise the most precious of American rights—the right to free speech and assembly. Rep. Giffords was doing the essential work of politics, meeting with her neighbors and constituents outside of a grocery store in a "Congress on Your Corner" gathering. This small "d" democratic act is so central to our Constitution and our republic that its protection is enshrined in the First Amendment, the same amendment that Giffords read aloud on the opening day of Congress.

Nothing is more corrosive to democracy than the use of violence to terrorize the public square, to shut down speech, to slay those seeking its exercise. Among the lives so wantonly taken was that of Christina Taylor-Green, a third-grader who had just been elected to her school’s student council. She died because of her love for political engagement. Her loss diminishes us all.

The rampage has led, as it should, to a broad indictment of the vitriol and venom on the right that has come to characterize too much of our political dialogue—particularly, since the election of Barack Obama. Arizona has been, as Pima County Sheriff Clarence W. Dupnik stated, "a mecca for prejudice and bigotry" and a hotbed of Tea Party anger and hatred toward immigrants.

John M. Roll, the chief federal judge of Arizona, killed in the rampage, lived with hundreds of death threats. Talk radio hosts fomented rage over his decision to allow to go forward a lawsuit filed by undocumented immigrants against a rancher. Giffords, a moderate Blue Dog Democrat, was demonized in her reelection campaign as a socialist, a communist, a fascist, a job-killer, a traitor and much more. Her office was vandalized after she voted in favor of Obama’s healthcare plan. On her Web page, Sarah Palin put Giffords’s district in the cross hairs of a gunsight, while Giffords’s Republican opponent invited supporters to "shoot a fully automatic M16" with him.

Mendacious and vicious rhetoric is destructive. Honesty, more tolerance and the jettisoning of violent imagery in our politics would be a good thing. Yet it’s worth reminding ourselves that passion and vitriol in political disputes are as American as apple pie—with a lineage tracing back to Tom Paine and Thomas Jefferson. Violent rhetoric is deplorable, but we still don’t know whether it was responsible for last weekend’s horror.

Editor’s Note: Read all of Katrina’s column here.