A blessed few are both glib and sincere, capable of convincing people of almost anything yet never making an argument that isn’t authenticated by their own emotional truth. This unlikely rhetorical formula seldom works when it counts—imagine it swaying al-Qaeda, the Gestapo, or the Inquisition—but it’s served Oprah Winfrey well. Unsurprisingly, Winfrey’s Harpo Films produced The Great Debaters, the latest uplift exercise to feature the ever-ingratiating Denzel Washington. He’s both the star and director of this feel-bad-then-good fable, based on the mid-’30s triumphs of the debate team from all-black Wiley College.

Like Antwone Fisher, Washington’s 2002 directorial debut, The Great Debaters is inspired by a true story. Yet the movie is closer to 2000’s Remember the Titans, a Washington star turn that grafted the names of real people and places to a fundamentally fictional tale. As in that movie, the actor in The Great Debaters plays a sometimes prickly but always righteous teacher. He’s Melvin B. Tolson, a real-life poet, professor, and labor organizer who led Wiley’s debate team out of rigidly segregated east Texas to challenge top squads from white schools. In 1935, Tolson’s debaters beat the national champion, USC. (The movie trades up, substituting Harvard for the California school.)

The Great Debaters has its strengths, including a smooth performance from Washington and a deeper one from Forest Whitaker, who plays the less confrontational James Farmer Sr., a Wiley professor of theology. The movie also effectively conjures the daily perils of being black in ’30s Texas, most graphically in a sequence where the traveling debaters happen upon a lynching. More revealing, though, is the scene in which some rural whites demand compensation from Farmer for a pig he allegedly ran over. The professor knows he’s defenseless, simply because he’s black and they’re white, but that’s not the whole dynamic. The mild-mannered Farmer is the worst kind of threat to the status quo: a respectably dressed, ­college-educated black man who’s clearly more refined than the bullies who’ve waylaid him.

The professor’s 14-year-old son, James Farmer Jr., is one of Tolson’s debaters. The younger Farmer, later a major civil rights leader, is another of scripter Robert Eisele’s genuine figures. Yet the film’s version of him (played by Denzel Whitaker, who’s not related to either of his namesakes) doesn’t seem any more authentic than his fictional teammates: Henry Lowe (Nate Parker), a smart guy with a compulsion to run to the closest juke joint whenever he’s under stress, and Samantha Booke (Jurnee Smollett), who is, well, the girl.

These thin characterizations hobble the movie, but its fatal defect is its refusal to respect the rules and goals of formal debate. Actual winning debate teams are logical and unemotional, and they must be prepared to assert either side of a case. The point is to be rationally irrefutable, not morally correct. Yet the Wiley debaters are never seen making a case with which they don’t agree, and that doesn’t directly reflect their own experience. Each match, in other words, is an episode of Oprah.

The last drops of plausibility evaporate when the Wiley team travels to Cambridge, Mass., to face Harvard and is housed in a posh suite whose African-American butler explains Gandhi’s idea of “Satyagraha” to them. Improbably, the challengers are assigned to argue for civil disobedience. Impossibly, Farmer wins the day with an utterly personalized speech that’s essentially a threat: “You should pray” that oppressed blacks choose nonviolent protest, a summation that might as well be accompanied by a clenched fist. In its quest to appeal viscerally to contemporary audiences, The Great Debaters forgets not only time and place but ultimately its subject. At least football players in Remember the Titans didn’t charge across the field wielding hockey sticks.