September 11 marked the 20th anniversary of 9/11, the deadliest terrorist attack in United States history. With the Taliban back in control in Afghanistan, Islamist extremism has been in the news a lot recently. Examining the history of terrorism and extremism in the U.S., liberal economist and New York Times columnist Paul Krugman does something that most of the far-right pundits at Fox News will never do: He looks at the big picture. And Krugman stresses that when it comes to terrorism in the U.S., most of the violence has come from domestic extremists — not foreign terrorists and radical Islamists.

“It may seem like a terrible thing to say,” Krugman writes, “but a fair number of people — especially in the news media — are nostalgic about the months that followed 9/11. Some pundits openly pine for the sense of national unity that they imagine prevailed in the aftermath of the terrorist attack. More subtly, my sense is that many long for the days when the big threat […]