The recent verbal attacks by the Republican presumptive nominee Donald Trump and his supporters on President Barack Obama for avoiding the phrase "radical Islam" in his public pronouncements are simplistic, racially inflammatory — and flatly misinformed. Settling upon accurate and strategically nuanced terms to describe the post-9/11 enemy is not the product of "political correctness" (contra Trump) or a failure to understand the enemy (contra a much-discussed Atlantic cover story). Nor are objections to using overly broad terms like "Islamic radicalism" limited to Democrats. The Bush administration understood the power of words, too. It concluded that distinctions that may seem...