Dylan Mathews has a post at Vox on Woodrow Wilson and race. IMHO he has two errors:
"Wilson himself was the descendant of Confederate soldiers..." According to Wikipedia, his father was briefly a chaplain in the Confederate army.
" Wilson lent The Birth of a Nation his approval by screening it at the White House and reportedly telling Griffith that it could "teach history with lightning.""
The bit about the quote is terrible. Yes, this has been reported, but it's dubious. Mathews links to the abstract of an article which promises to examine the history of the quote. The article is behind a paywall so Mathews should give us the article's conclusion, not an abstract.Other sources question the quote. See Snopes
[updated. See footnote 25 from this source.[