The documentarian’s brisk, enjoyable new film contains the curiously contentious final interview with David Cornwell, a.k.a. John le Carré. Photo: David Appleby Documentarian Errol Morris’s interviews are rarely adversarial, but there’s a challenge implicit in them — the promise that their subjects will not just be examined from all angles but also, when necessary, pushed. “Have you ever thought that you might be wrong?” he asked Fred A. Leuchter Jr., the execution-equipment specialist turned Holocaust denier of Mr. Death, and got the astounding response of “No, I’m past that.” The potential for confrontation has felt more urgent whenever he’s turned...