DW Griffith's silent epic lionised the Ku Klux Klan and depicted black Americans as ignorant rapists, but cinema still owes a debt to the director's pioneering techniquesThe birth of cinema was brutal and ugly, and the photographic evidence comes with a health warning attached. The Birth of a Nation, directed by DW Griffith back in 1915, has a reputation as one of the greatest movies ever made – and one of the most purely vile.