THE MOVIE “Selma” takes us back half a century to one of the most stirring and momentous events of that era: the march that helped secure passage of the Voting Rights Act of 1965, finally bringing the franchise to millions of people who supposedly had been granted it nearly a century before. Some have criticized the film for attributing to President Lyndon B. Johnson a couple of actions for which there is little or no historical evidence. Some have speculated that it got fewer Academy Award nominations than it deserved, in part because of the controversy over whether it contained distortions of history.

But the truth is that Lyndon Johnson’s stature as a champion of civil rights legislation will survive any movie misrepresentation, and “Selma” will, we’d guess, be watched for years to come — on screens, phones and devices yet to be invented — as an inspirational tale of a great American leader, the Rev. Martin Luther King Jr.

The truly history-making significance of that bloody police assault on peaceful marchers at Selma, Ala., 50 years ago lies in the discrediting of a far more pernicious distortion of history, one that became firmly established in parts of the country and was accepted, if not endorsed, by much of the rest of society. It began after Reconstruction, the brief period following the Civil War when newly freed slaves gained the right to vote and, in many places, elected black people to office. Reconstruction was ended by violent resistance from many white Southerners and by a general lack of will in the rest of the country to pursue the business of racial justice any further. A new mythology was created to discredit the short-lived venture in black participation in government: Reconstruction rule was portrayed as dictatorial and black officeholders as uniformly corrupt and incompetent.

This “history” was represented in films such as “Birth of a Nation” and (less malevolently) “Gone With the Wind.” It permeated many other parts of popular culture, was accepted as largely true in school textbooks in many parts of the country and influenced some of our proudest national institutions in ways that shame us to this day: West Point, for example, had no black cadets after Reconstruction until 1932, when Benjamin O. Davis (later to command the Tuskegee Airmen) was admitted, and then spent four years being shunned by his classmates.

Underlying all the hurtful discrimination, of course, was force and violence, whether official, unofficial or a combination of the two. It took the form of unequal justice in the courts and on the streets, and of community-sanctioned murder by lynch mobs, often horrifying spectacles of depravity. If cameras had been everywhere, as they are now, perhaps things would have been different. The shock of a beating or an extrajudicial murder has proved to be far more intense when witnessed than when we read about it in the newspaper or hear of it on radio.

One great accomplishment of Martin Luther King and those who served with him in America’s civil rights revolution was to recognize the power of the new media: Americans could see the face of Rosa Parks on film, the bus boycotters, the murder of children in Sunday School, the brutal attack on the Selma marchers with fire hoses and attack dogs — peaceable demonstrators battered and beaten for seeking their constitutional rights in a vicious display of force that appalled the great mass of Americans. It was a morality play on film whose truth and effectiveness are beyond dispute, though it has many scenes still to be played.