On July 29, President Trump tweeted: “Just remember, Iranians never won a war, but never lost a negotiation.” In just 12 words, Trump leveled a multi-layered, ahistorical insult against both his predecessor, Barack Obama, and Iran. More importantly, the remarks betray a dangerously ignorant understanding of Iran that could result in another careless Middle East war of choice. The tweet invokes a clichéd, colonial-era stereotype that Iranians, like other Middle Eastern peoples, are wily swindlers—rapacious, greedy bazaar merchants who aim to take advantage of honest and unsuspecting Westerners. Trump is hardly the first American leader to dabble in such denigrating...