Between September 11, 2001 and March 2014, right-wing extremists killed 34 people in America. If you count the three Jewish community members Frazier Glenn Cross killed in Kansas City before screaming "Heil Hitler" as police arrested him this past April, the tally jumps to 37. And it hits 40 when you add the two policemen and lone civilian who died this weekend when Jerad and Amanda Miller launched their Las Vegas revolution. The officers were eating lunch at a pizza restaurant, treading on no one, when they were shot dead and draped in a Gadsden flag. The civilian at the nearby Wal-Mart, Joseph Wilcox, was armed and ready to put an end to Jerad's rampage, but didn't know Amanda was armed as well. Turns out a good guy with a gun is the only way to stop a bad guy with a gun, unless the bad guy's wife happens to have a gun, too.

The above figures are based on a tally maintained by experts at the New America Foundation. They array their analysis in a way that makes the implicit point that, for all our fretting about jihadi extremism, it's been less deadly in the U.S. since 9/11 than domestic terrorism, but that neither problem is particularly dangerous.

And it's true. There are 320-or-so million people in the United States, over 30 million more than lived here on September 11, 2001. Forty people isn't very many. Among causes of death in the U.S., right-wing violence must rank near the bottom.

But 40 people is more than zero people, which is the number that have been killed by left-wing extremists over the same stretch. As NAF's Peter Bergen wrote recently, "although a variety of left wing militants and environmental extremists have carried out violent attacks for political reasons against property and individuals since 9/11, none have been linked to a lethal attack."

Something must account for the difference. The violent right in America might not be a huge threat to public safety, but it still has a body count.