"Clearly, Griffith believed it in his interest to have the president appear to legitimate the “history” in Birth. This explains both the special showing of the film at the White House and the quotations form Wilson's earlier historical work. An examination of the intertitles and what Wilson had actually written suggests, however, that Griffith was at the very least rather inexact in the quotations he used and that, in each case, his selective excerpts altered to a degree the original meaning...Although Wilson plainly sympathized to a considerable degree with the South (he had grown up in Virginia), his *History* was in reality much more balanced in his discussion of Reconstruction than Griffith would have wished...." Melvyn Stokes, *D. W. Griffith's The Birth of a Nation: A History of the Most Controversial Motion Picture of All Time,* p. 198.
https://books.google.com/books?id=fGJFpiTjbKwC&pg=PA198 Stokes continues,
"Where Wilson differed most from Griffith was in his treatment of the Ku Klux Klan. The Klan had been, Wilson observed, 'a very tempting and dangerous instrument of power for days of disorder and social upheaval.' In the beginning, 'sober men' had advised upon and curbed the activities of the hooded order. As time went on, however, such control proved increasingly impossible to exercise as the Klan was drawn deeper and deeper 'into the ways of violence and outlawry. 'Men of hot passions who could not always be restrained,' Wilson commented, 'carried their plans into effect. Reckless men not of their order, malicious fellows of the baser sort who did not feel the compulsions of honor and who had private grudges to satisfy, imitated their disguises and borrowed their methods.' The number of abuses grew: 'Brutal crimes were committed; the innocent suffered with the guilty; a reign of terror was brought on, and society was infinitely more disturbed than defended.' In contrast with Griffith's later film, which depicted the Klan as rescuing white women from the threat posed by black men, Wilson made it clear that the Klan itself arracked female targets. 'The more ardent regulators,' he wrote, 'made no nice discriminations. All northern white men or women who came into the South to work among the negroes, though they were but school teachers, were in danger of their enmity and silent onset.' According to Wilson, the Klan was deeply unchivalrous. It was also shortlived and relatively unsuccessful. Instead of overthrowing Radical regimes and restoring white suprmeacy by force, as *The Birth of a Nation* suggested, the original Klan had been effectively destroyed by new federal laws of 1870 and 1871 and the determined actions of President Grant.."
https://books.google.com/books?id=fGJFpiTjbKwC&pg=PA200