In 2013, Ben Carson gave a speech at the National Prayer Breakfast that launched his political career. According to the rapturous response on the Internet, Carson’s remarks were a rebuke of President Obama—people saw Carson as an authentic black counterpoint to the President—but they were just as clearly a rejection of what he called the culture of “political correctness.” “The P.C. police are out in force,” he warned from the podium. “We’ve reached a point where people are afraid to say what they think because someone might be offended. People are afraid to say ‘Merry Christmas’ at Christmastime.”

The concern among the burgeoning numbers of political-correctness critics—on both the left and right—is that the parameters of polite (or at least non-bigoted) discussion get in the way of truth-telling, leaving us with good feelings and palliative falsehoods. There is, however, a logical fallacy at play among many of these opponents, in their presumption that the validity of a statement exists in direct proportion to its capacity to offend.

There are few anodyne truths in Ben Carson’s worldview. The decibel of the objections is evidence that he’s struck upon truth. A hit dog hollers, as Southerners say. When, this past Sunday, on “Meet the Press,” Carson voiced his opposition to the idea of a Muslim being elected President, he did so in the same calm, measured tones that attend almost all of his pronouncements. He spoke with the quiet confidence of a man convinced of the rectitude of his own position. Here is Carson responding to a question about whether voters should consider a candidate’s faith:

I guess it depends on what that faith is. If it's inconsistent with the values and principles of America, then of course it should matter. But if it fits within the realm of America and consistent with the Constitution, no problem.

Carson went on to say that he believes that Islam is inconsistent with the Constitution, but that, inexplicably, he has no problem with Muslims serving in Congress.

Carson’s position within the paranormal wing of the G.O.P. is perplexing for a number of reasons. Unlike Donald Trump, who is capable of making equally inflammatory and nativist comments, Carson's intellectual accomplishments are indisputable.* He is a product of the most respected educational institutions in the United States and was once a foremost practitioner in a highly complex field of medicine. Yet his virtuoso abilities coexist with a loosely tethered relationship to other types of rational thought. Carson is a scientist who disavows evolution, a citizen who professes to be deeply concerned about democracy yet supports a religious litmus test for public office, and a physician who devoted himself to saving the lives of children but indulges the hypertensive claims of the anti-vaccine element. His bifurcated thinking calls to mind James Watson, the Nobel winning co-discoverer of DNA, who spent years mouthing racist and sexist theories of human intelligence. On the stump, Carson seems like an object lesson in what happens when STEM majors don’t take enough courses in the humanities and social sciences.

For reasons connected to his race, his education, and his exceptional talent, Carson at first carried an imprimatur of Serious Thought that the others in the crowded G.O.P. field did not. (Building a real-estate empire, winning a Senate seat, and serving as a corporate C.E.O. are impressive accomplishments, but they are literally not brain surgery.) But Carson’s duelling intellect and paranoia have led him to support untenable positions with minor qualifications. He panders by faint dissent. By stating that he believes that Islam is inconsistent with American democracy and that President Obama is a Christian born in the United States, he validates the substance of birtherism, just not this specific instance of it. When Carson was confronted, during the last Republican debate, with the question of whether vaccines cause autism, he stated that they did not but offered paranoiacs the nebulous chaser that we are giving children too many immunizations. The suggestion that vaccines have some nebulous danger essentially nullified the statement that preceded it.

That the party responsible for the Southern strategy, the racist populism of the Reagan era, and the current age of voter suppression can count a black neurosurgeon among its most popular Presidential candidate is in itself a form of vaccination against charges of racism. It means one thing when a white billionaire taps into whites’ anxieties about cultural and economic displacement, and something else entirely when a black man from Detroit validates their conspiratorial fears about the Affordable Care Act. Or when, in an oblivious echo of the Dred Scott decision, an African-American states that entire segments of the population are irreconcilable with the Constitution. Carson’s is not a novel act. Five years ago, Juan Williams, a black journalist who covered civil rights and wrote a biography of Thurgood Marshall, stated that he felt fearful when boarding a plane with Muslims. The ensuing outcry was, predictably, denounced as political correctness.

The enduring legacy of Carson’s candidacy, however it ends, is likely to be the recognition that, under certain circumstances, cynicism is less of a problem than sincerity. Would that such detached thinking, from so talented a figure, came with a wink and a nod—that it were simply a matter of demagogic competition in a crowded political field. But Carson appears to mean what he says, and there is a consistent market for his brand of exonerating racism, for bigotries so valid that even a brilliant black man endorses them. His certainty that the din of outrage is merely the yelping dog of political correctness prohibits him from fulfilling one of the primary responsibilities of a scientist: the honest evaluation of contrary data. It also blinds him to the widely apparent truth that his politics are not simply incorrect—they're also wrong.

*A previous version of this sentence mischaracterized Ted Cruz’s academic achievements.