Back in April, the Homeland Security Department (DHS) came under heavy rhetorical fire from some politicians and commentators. They were infuriated by an intelligence analysis warning that the political and economic climate could spur outbreaks of far-right extremism. As TalkingPointsMemo notes, Rep. Michelle Bachman, R-Minn., accused the department of defining gun-rights advocates, among others, as extremists.

Nevertheless, that DHS report may look more prescient than politically biased today, TPM and other commentators, including True/Slant's Ryan Sager, argue. Steve Benen of The Washington Monthly joins in as well. The suspect in the Wednesday killing of Stephen T. Johns, a guard at the U.S. Holocaust Memorial Museum in Washington, is an elderly Maryland resident with a long history of anti-Jewish and anti-black activities, and an attempted hostage-taking at the Federal Reserve in 1981. The Southern Poverty Law Center, one of the leading monitors and analysts of far-right extremists, provides even more detail about the alleged killer's past.

Accused perpetrators in other recent deadly outbursts of extremist violence also seem to have been steeped in the far-right political culture. Scott Roeder, the accused killer of abortion provider Dr. George Tiller of Wichita, Kan., was reported to have belonged in the past to an anti-government "militia."

In May, a CQ Researcher report, "Hate Groups" cited other examples from recent months. The report also delved into the controversy over the DHS report, and provided a historical overview of far-right extremism in this country. It's an eventful history, and the events haven't ended.