More recently, in the 1990s, Republicans assailed President Bill Clinton’s efforts to negotiate a nuclear deal with North Korea, with Senator John McCain calling the process tantamount to “appeasement.”

In 2003, when Iraq began spiraling into chaos, Deputy Secretary of Defense Paul Wolfowitz received a memo suggesting that the United States engage disaffected Sunnis. He reportedly returned it with three words scribbled in the margin: “They are Nazis!”

In 2008, President George W. Bush told the Israeli Knesset, “Some seem to believe that we should negotiate with the terrorists and radicals, as if some ingenious argument will persuade them they have been wrong all along.” But this contention, he said, was only “the false comfort of appeasement.”

For a decade after the United States invaded Afghanistan, the Bush and Obama administrations refused to engage the Taliban insurgents. A major review of U.S. strategy in 2009 didn’t even consider the option of a diplomatic solution with the Taliban leadership. In 2010, U.S. Special Representative for Afghanistan Richard Holbrooke asked General David Petraeus about Afghan reconciliation. “Richard, that’s a 15-second conversation,” Petraeus reportedly responded. “Yes, eventually. But no. Not now.” Later, during the 2012 presidential campaign, the Republican presidential candidate Mitt Romney declared: “We should not negotiate with the Taliban, we should defeat the Taliban.”

Resistance to diplomatic engagement is usually strongest on the political right. In 2013, for example, 27 percent of Democrats disapproved of an interim agreement with Iran on its nuclear program—compared with 58 percent of Republicans. Democratic presidents are particularly vulnerable to attack as “appeasers” for talking to enemies. By contrast, it’s often politically easier for hawkish Republicans to negotiate because few doubt their toughness. During the Cold War, Democratic presidents started the big wars in Korea and Vietnam. And Republican presidents talked America’s way out of them. As the saying goes, it took a Nixon to go to China.

Why do Americans dislike negotiating with enemies? The answer has to do with the country’s combination of power and moralism. After 1945, the United States bestrode the world like a colossus, with an economy three times larger than that of its nearest competitor, the Soviet Union. America’s globe-girdling capabilities diminished the apparent need to compromise with weaker opponents like North Vietnam, which Lyndon Johnson called a “raggedy-ass little fourth-rate country.”

Meanwhile, according to a moralistic strain in American culture, compromising with 'evil' opponents sullies U.S. values. Americans tend to be deeply committed to the nation’s ideals of democracy and individual rights. Rates of religiosity are also far higher in the United States than in other rich democracies. As a result, Americans are more likely to say there are absolute standards for good and evil than Europeans, Canadians, and Japanese, who are more likely to say that ethics depend on circumstances.