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 in real life – imagine trying it on al-Quaida, the Gestapo, or the Inquisition – but it has served Oprah Winfrey well. Naturally, 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-1930s triumphs of the debate team from all-black Wiley College.

Like Antwone Fisher, Washington’s directorial debut, The Great Debaters is inspired by a true story. Yet the movie is closer to Remember the Titans, another Washington vehicle that grafted the names of real people and places to a fundamentally fictional tale. As in that movie, the actor 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. This movie trades up, substituting Harvard for the California school. But that cheat is not the major problem.

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 everyday peril of being black in 1930s 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 down. 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 the refusal to respect the rules and goals of formal debate. Actual winning debate teams are logical and unemotional, and 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.

The last drops of plausibility evaporate when the Wiley team travels to Cambridge 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 non-violent 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 also, ultimately, its subject. At least Remember the Titans’ football players didn’t take the field carrying hockey sticks.

THE GREAT DEBATERS ( 2 ) Directed by Denzel Washington • Starring Denzel Washington, Denzel Whitaker and Forest Whitaker • PG-13, 123 min • At the Maya Cinemas, Osio Cinemas.