The original film was very prophetic:
Stoneman and his protégé Silas Lynch, a mulatto exhibiting psychopathic characteristics,[17] travel to South Carolina to observe the implementation of Reconstruction policies firsthand. Black occupation soldiers are seen parading through the streets and pushing white residents aside on the sidewalks. During the election, in which Lynch is elected lieutenant governor, whites are seen being prevented from voting while blacks are observed stuffing the ballot boxes. The newly elected, mostly black members of the South Carolina legislature are shown at their desks displaying inappropriate behavior, such as one member taking off his shoe and putting his feet up on his desk, and others drinking liquor and feasting on stereotypically African American fare such as fried chicken. The legislature passes laws requiring white civilians to salute black soldiers..................
https://en.wikipedia.org/wiki/The_Birth_of_a_Nation
But I will add this speaks more to the nature of man than it does to race.