Nate Parker’s “The Birth of a Nation” tells the story of an enslaved Southern preacher, Nat Turner, who in 1831 led a bloody revolt against white plantation owners. It was a failure that led to no immediate positive change and, in fact, sparked a wave of retaliatory murders of innocent blacks. Turner himself is not the most clear-cut hero. So why make a movie about him?

Cinematically, the subject is irresistible. Parker, who plays Turner, is a 36-year-old actor with a modest resume of ensemble films like “Red Tails” and “The Great Debaters.” Yet he also co-wrote and directed “The Birth of a Nation,” which sold at Sundance for $17.5 million, a festival record. The film’s audacious title — the same as D.W. Griffith’s notoriously racist magnum opus of 1915 — suggests that Parker has more on his mind than just career-building. As the outcry over the mostly white Oscars grew earlier this year, Parker called his movie “a blow against white supremacy and racism.”

“The Birth of a Nation” is certainly a riveting and unsettling movie about the rage and despair that defined black existence in the Antebellum South. Turner, the rare literate slave, begins the film as a docile lackey whose owner, Samuel Turner (a very good Armie Hammer), rents him out to preach obedience to other slaves. Turner does as he’s told, quoting scripture to the malnourished, the beaten, the half-dead. In one harrowing scene, he watches a slave’s teeth being chiseled out to ease force-feeding.

Turner’s eventual epiphany has an intriguing ring of madness. After the rape of his wife, Cherry (Aja Naomi King), the preacher’s rhetoric turns fiery. He speaks of freedom, but it’s clear that those who join him are driven mostly by desperation and an understandable thirst for revenge. Although the movie invents some incidents (Turner’s wife was not raped) and omits others (such as the murders of white children), Turner emerges as a discomforting and tragic figure who we cannot help but sympathize with.

Parker himself may be something less than a hero. He’s been dogged by a 1991 rape charge that ended in acquittal; his accuser killed herself in 2012. That back story will surely haunt “The Birth of the Nation” during its Oscar campaign, which, like Turner’s rebellion, may amount to only a symbolic victory.