For the many people who have grown up accustomed to an integrated society, affirmative action and now an African-American president, America’s dark history of racial division may seem distant and surreal. It’s hard to believe that just 50 years ago, sitting at the lunch counter at a Woolworth’s could spell a death sentence for a young African-American.

On Feb. 1, 1960, four college freshmen confronted that risk and answered the question posed by one among them, Joseph McNeil: “When is it going to stop? Who’s going to stand up and say no?”

Their story is retold movingly in “Seizing Justice: The Greensboro 4,” which will have its television premiere Sunday — 50 years to the day after Woolworth’s gave in to the pressure of the mushrooming sit-in movement and desegregated all of its stores.

“There were people who had sit-ins before, but they weren’t really successful,” said Lynn Kessler, who wrote and produced the film. She said other sit-in movements lacked the persistence of the Greensboro Four, who she said inspired about 70,000 people to join sit-in movements around the country within six months.

“What’s really important is to remember how quickly people forget,” said David Royle, executive vice president of programming and production for the Smithsonian Networks, which collaborated on the film. “When you talk to young people today, they don’t always understand just how important these movements were in bringing about change.”

Certainly most striking to those who didn’t live through that period is the level of violence that was visited upon blacks who dared to resist their oppressors. The film does not shy away from that theme, repeatedly showing images of hanged black men and the open casket of Emmett Till, a 14-year-old black boy whose brutal murder in 1955 helped ignite the civil rights movement.

“We’d get constant threats, sometimes 10 or 12 a day,” said Jibreel Khazan, one of the four students. “Someone would call the telephone in our dormitory and say, ‘Nigger, we’re going to kill you tonight.’ I’d say, ‘Well let me know when you’re having a party so I won’t go!’ We had to laugh at it because if we took it seriously, that would stop us from achieving our goals.”

The four students faced a culture that was not only violent but so pervasive that on the first day of their sit-in, an old African-American woman working behind the counter told them to stop what they were doing.

From the beginning, they vowed to confront that culture with simple focus and persistence instead of violence.

Practicing nonviolent responses, Khazan said, “helped us deal with the chaos that was taking place around us.”

Footage in the movie shows mobs of white people forming behind blacks seated at counters, yelling, spitting, pouring drinks on them, pushing them over the counter or pulling them to the ground and beating them. Each humiliation is met with a composure that is at once both sad and dignified.

In one clip, a white man is kicking a black man on the ground, as the black man rolls from side to side, covering his head. The aggressor pauses, not knowing what to do with a victim who won’t retaliate, when another white man steps in to break it up.

“Nonviolence has to be learned,” said Khazan, formerly Ezell Blair Jr. “When every organism is born, it fights to stay alive. In us is the urge to fight to live. We take it a step farther when we attack each other. To live a life of nonviolence is a high level of art and science.”

When asked what thoughts he used to get through the abuse that he took at the lunch counter, McNeil said he maintained “a strong moral commitment, and the faith that if you’re going to put yourself in harm’s way for a cause, there couldn’t be a better one.”

A four-stool section of the Woolworth’s lunch counter sits in the National Museum of American History, a piece of furniture brought to life by the brave young men who sat there.

“Without [them],” museum Director Brent Glass said, “this counter would mean nothing.”

“Seizing Justice,” a production of CBS and the Smithsonian Channel, will be shown at 8 p.m. Sunday on the Smithsonian Channel.