One of the biggest reasons for the resurgence of the Klan during the 1920s is that they had a very powerful and influential supporter: President Woodrow Wilson. One historian has noted that Wilson's "stance on race is perhaps the greatest single defect of his moral vision of what the United States should be." During his administration, federal offices were segregated, interracial marriage was declared a felony, and he was himself a member of the Ku Klux Klan.
About segregation, Wilson is reported to have that it is "not a humiliation but a benefit, and ought to be so regarded." When African Americans began to complain about his policies, he told The New York Times, "If the colored people made a mistake in voting for me, they ought to correct it."
Wilson was an enthusiastic supporter of D.W. Griffith's film "Birth of a Nation." According to Charles Paul Freund:
He arranged for preview screenings for his cabinet, for Congress, and for the Supreme Court, and he gave Dixon and Griffith an endorsement they could exploit. "It is like writing history with lightning," Wilson said of this KKK celebration, "and my only regret is that it is all so terribly true." The first half of Wilson's endorsement is still affixed to prints of the film that are screened for film students studying Griffith's advances in editing.
I hope this helps you.