Anyone who thinks that this film depicts real history is seriously deluded. One commenter noted that the KKK was fighting for a good cause during Reconstruction, but not now. I guess to him good causes include killing and intimidating freed slaves who were merely attempting to exercise their rights to vote and make a living.
Griffith's portrayal of Reconstruction black politicians is not only racist, but blatantly untrue. Only in rare instances and for a short time did black representatives control any Southern legislatures, and this at a time when they were the majority of voters in many Southern states! For years teachers of Reconstruction have emphasized carpetbaggers, but have ommitted the fact that the post-Reconstruction governments were founded with the explicit purpose of disenfranchising blacks and violently enforcing their underclass status. For this reason and others, Birth of a Nation's claims to historical accuracy would be comical, if not for the horrific implications of the film.
That said, this film should be seen, mainly because it provides a document of a poisonous way of thinking that is by no means dead. It also represents the pop cultural moment when Northern and Southern whites reconciled over the memory of the Civil War, mainly to the detriment of blacks. Lastly, those who want this film burned only give ammunition to the idiots who still praise the KKK. It's better to let these jerks hang themselves with their own rhetorical ropes than to let them claim victim status.