Know-Nothing American History
I know full well that this Jack Hitt piece in The New Yorker is satirical, but it hits close to home. When a movement increasingly derives its news from Fox and its history from partisan publishers -- especially ones with a massive financial incentive to portray their ideological opponents in terms that respectable people would find beyond the pale -- things get out of hand.
That's how you get books like David Limbaugh's "The Great Destroyer: Obama's War on the Republic" and Dinesh D'Souza's "2016: Obama's America." They're both utter nonsense, but they play perfectly to people who don't know any better.