"But Griffiths’ film has almost no truth in it — and it is monstrously, numbingly racist. Its black characters are drunks and rapists, played by gurning white actors in blackface, while the Ku Klux Klan are shown to be saviour knights of the new republic. Think again of that strange lack of films about American slavery, and wonder how long it will take for cinema to exorcise these demons. In that light, 12 Years a Slave isn’t simply a masterpiece, it’s a milestone. This, at last, really is history written with lightning."

http://www.telegraph.co.uk/films/2016/06/03/12-years-a-slave-review-this-at-last-really-is-history-written-w/

D.W. Griffith's film is completely unrealistic and racist towards African-Americans depicted in the movie. It creates the idea that the Ku Klux Klan were saviors for killing the crude black characters. This movie has helped cause the lack of slavery movies over the years. Because of this, 12 Years a Slave isn't just a great depiction of slavery, it is a breakthrough in cinematic adaptations of slavery and history.