In an interview published on Sunday, Arkansas Republican Sen. Tom Cotton declared that “We have to study the history of slavery and its role and impact on the development of our country because otherwise we can’t understand our country. As the Founding Fathers said, it was the necessary evil upon which the union was built.”

What Cotton did not say is that the defenders of hideous acts almost always engage in this rhetorical tic, using that exact word: “necessary.”Join Our NewsletterOriginal reporting. Fearless journalism. Delivered to you.I’m in

Here are several notable examples:

• From 1986 to 1989, Saddam Hussein’s government conducted what it called the “Anfal” campaign against Kurdish Iraqi citizens in northern Iraq. In addition to firing squads and mass conventional bombings, the Iraqi military used mustard and nerve gas against civilians. Perhaps 150,000 people were murdered.

The Anfal campaign has been recognized by the British, Norwegian, and Swedish governments as genocide, and it was one of the crimes for which Saddam Hussein stood trial in 2006.

Before […]