Why D.W. Griffith's movie Birth of a Nation was so controversial.?

D.W. Griffith's "Birth of a Nation" was controversial primarily due to its portrayal of African Americans and its sympathetic depiction of the Ku Klux Klan. The film perpetuated racial stereotypes and glorified the KKK's violent actions during Reconstruction, which sparked outrage among civil rights groups and led to protests. Additionally, its innovative cinematic techniques were overshadowed by the harmful social implications, making it a pivotal yet divisive work in film history. The film's release in 1915 reignited racial tensions in the United States and influenced public perceptions of race for decades.