Christopher Hitchens and Douglas Wilson spend several days on the road together, debating the question that gives their co-written book its title: is Christianity good for the world? Director Darren Doane films the formal stops on college campuses, but just as much time goes to the two men arguing in cars, on planes, and over meals between venues, where the sparring turns looser and more personal. Hitchens, the atheist author of "God Is Not Great," and Wilson, an evangelical pastor and theologian, do not soften their positions for the cameras, but they also strike up something like a friendship on the tour, needling each other's arguments while sharing drinks and jokes. The film cuts between debate-hall footage, where each man works a crowd, and the in-transit conversation, where the same arguments get tested without an audience. It ends up being less a record of who won a debate and more a study of what genuine disagreement between two sharp, likable people actually looks like up close.