D. W Smith's movie, Birth of a Nation was so controversial because of many reasons.
First, it was a movie during the Civil War about two families, Union and Confederate and their relationship with each other. The movie was a blockbuster as it was viewed by more than four million people by 1922.
It was a groundbreaking movie because of its cinematography which was ahead of its time as night shots and parallel editing were used to great effect to show war scenes and also its sheer number or extras hired.
One major reason for its controversy was its blatant racism because it portrayed black men as r apists, murderers and people not deserving of human rights and are justified to be lynched.
A major cause of the Protestant Reformation was the sale of indulgences by the Catholic Church. Martin Luther began early in his writings criticizing this practice in saying that the Pope had no authority or right to sell this type of indulgence.