Alyssa Rosenberg blogs about pop culture for The Post’s Opinions section at washingtonpost.com/blogs/act-four/.

Seven months ago, Nate Parker seemed poised for a breakout year. “ The Birth of a Nation ,” his movie about Nat Turner’s slave rebellion in 1831, sold for a record price at the Sundance Film Festival and generated high-frequency Oscar buzz, especially after a year when the awards were slammed for their overwhelming whiteness. Instead, Parker’s rise drew attention to a 17-year-old rape case, which has made him the catalyst for another uncomfortable conversation about art and politics.

The entertainment industry has long shown a convenient willingness to separate the art from the artist; actors rush to work with Woody Allen and Academy members cheer Roman Polanski’s “The Pianist.” But with “Birth of a Nation,” messenger and message were on a collision course — one that forces us to reckon with the standards we set for artists who want not only to sell their work but also to lead Important National Discussions.

Parker’s chance to do that seems to be receding: Last week, the American Film Institute canceled a screening of the movie and the Toronto Film Festival conspicuously left a news conference on “The Birth of a Nation” off its roster. Some Academy members huffily suggested that they can’t watch a movie by this accused rapist.

The allegations that threaten to derail Parker’s project follow a depressingly familiar script for college sexual assaults involving athletes and alcohol. In 1999, Penn State wrestlers Parker and Jean Celestin, who has a story credit on the film, were accused of rape by a fellow student, who said she was too drunk to consent.

At trial, Parker, who had previously had sex with the victim, was acquitted, while Celestin was convicted. He won an appeal and the prosecutor chose not to retry the case. Later, the victim sued Penn State, saying that the university failed to protect her when Parker and Celestin harassed her after she came forward. She settled with the university for a small sum. In 2012, she committed suicide.

Parker’s acquittal means that he’s been free to build a career as an actor, director and producer. That’s as it should be; an acquittal ends the story, at least as a legal matter.

“The Birth of a Nation” was supposed to be the start of a new chapter, for Parker and for Hollywood. After the film’s triumphant Sundance debut, it assumed an elevated role. Parker’s unsparing look at slavery and rebellion was supposed to edge forward our deadlocked conversation about race. And Parker was poised to become the sort of multi-threat talent the Academy could embrace, and thereby redeem itself — partly, at least — for the sin of having failed to recognize black artists in previous years.

Accordingly, the film’s distributors planned a publicity tour that would swing through schools and churches, bolstering the idea that “The Birth of a Nation” was an important movie as well as a good one. Yet that sort of weighty message inevitably draws attention to the fitness of the messenger — especially because the movie treats the rape of Nat Turner’s wife as a significant motivation for the character.

Parker’s decision to give an interview about the rape case seemed designed to head off criticism. Instead, his statements have been clumsy and, at times, offensive.

He presents his “five daughters” and “lovely wife” and “four younger sisters” and a “mom [who] lives here with me” as some kind of proof of his goodness. He has described his alleged campaign of intimidation as youthful zealousness: “I see now that I may not have shown enough empathy even as I fought to clear my name.” And he’s brushed aside the idea that addressing the accusation and trial directly would have some value, insisting that “I can’t control the way people feel.”

But if Parker wants to remain a messenger, rather than a mere filmmaker, there’s more he could do to prove himself worthy of the role. He could explain how he thinks colleges should handle cases like his own, beyond “educating men and persecuting them when things come up,” a singularly unfortunate choice of words. He could discuss what he has learned about power, sex and consent in the years since, and how they informed his treatment of rape in “The Birth of a Nation.” And if he really wants to “lead charges against injustice against people of color, against the LGBT community,” he could put some of his movie money where his mouth is and pledge his profits to the causes he says he cares so much about. Reducing the rape kit backlog would not be a bad start.

As for the rest of us, industry leaders and ordinary viewers, we could spend a little less time smugly condemning Parker’s behavior and more effort considering what specific, substantive things we can demand from the people who want to earn our admiration and our trust. Turning our backs on his movie might make us feel superior. But given the position Parker’s in, we can ask for a whole lot more. If Parker and men like him want to lead movements, we have an opportunity to remind them that change has to start with their own behavior.