“But he’s Black! The role isn’t written for a Black man,” sputtered “Lethal Weapon” film director Richard Donner during the casting process for one of Hollywood’s lucrative franchises.

“So what?!” shot back iconic casting director Marion Dougherty, “He can act.”

The struggling actor was Danny Glover, and the late, great Dougherty knew talent. She worked from her gut instincts.

Tom Donahue’s documentary “Casting By” chronicles the evolution from studio contract players to the boom of creative casting in the 1970s, with Marion Dougherty leading the charge in that shift.

Produced by Kate Lacey, Ilan Arboleda and Joanna Colbert and directed by Tom Donahue, “Casting By” puts the glitzy Hollywood spotlight on filmmaking’s unsung heroes—the casting directors—and takes the lucky viewer through a fascinating journey through half a century of Hollywood history.

Editor Jill Schweitzer is at the top of her game, blending long-forgotten, vintage footage and personal narratives by significant industry players including Martin Scorsese, Woody Allen, Clint Eastwood, Glenn Close, Robert Duvall, Al Pacino, Robert De Niro, Mel Gibson, John Travolta and Glover.

Dougherty pioneered a significant shift in casting and groomed a new generation. Casting vets Juliet Taylor, Ellen Lewis and her West Coast counterpart Lynn Stalmaster share and give rich credit where rich credit is due.

That level of intuitiveness helped change the unjust old studio system and usher in New Hollywood with movies like “Midnight Cowboy,” “The Graduate,” “Butch Cassidy and the Sunshine Kid” and “Bonnie and Clyde.”

Television, a new medium at the time, allowed these casting trailblazers to break away from typecasting and give opportunities to James Dean, Dustin Hoffman, Bette Midler, Cicely Tyson, Gene Hackman and others.

Dougherty’s office was housed in a brownstone in New York City and was often jokingly compared to a friendly brothel. Every room was brimming with creative life and served as a safe haven for some of film’s greatest contributors.

The rich and continuous legacy of the role of the casting director is undeniable, and yet, there isn’t a Academy Award to highlight their contributions to the art form.

“Casting is a high art when you run into a Marion Dougherty.” Those sentiments are repeated over and over again throughout the film, ironically by several Oscar winners.

The fact that casting is the only main-title film credit not recognized with an Oscar category is a sore point that’s raised with eloquence in Donahue’s highly entertaining documentary.

Yet, when pillars in the industry attempted to have a special Oscar dedicated to Doughety, the board denied their passionate requests.

“The board, like Hollywood, is run by the old white boys club” revealed Doughety.

“I’m ashamed to admit it, but she pointed out my prejudice and it changed my life,” Donner shared regarding the eventual casting of Glover.

“The creation of ‘Casting By’ was a collaborative process made in the spirit of the late Marion Dougherty to recognize these unsung heroes. We could not be more excited to have found the perfect home for our film at HBO,” said Donahue.

I give it eight stars: Four because it’s entertaining and informative, and four for the short-sighted snub of the Oscar voting committee.

“Casting By” debuts Monday, Aug. 5.