This is an adapted excerpt from the Nov. 9 episode of “Velshi.” On Feb. 18, 1915, President Woodrow Wilson screened a film for senior government officials in the East Room of the White House. It was called “Birth of a Nation,” a three-hour piece of propaganda that glorified the Ku Klux Klan and portrayed emancipated Black Americans as unworthy of freedom. Today’s Republican Party has moved beyond the dog whistle, openly aligning with forces that once existed only in the darkest corners of the internet. It marked a chilling inflection point in the U.S., when white nationalism stepped out of...