I trust that at least one very contemporary example of this comes readily to mind.
But if that’s the only example you can think of — if you’ve forgotten Pizzagate and birtherism and Obama’s-a-Muslim — or if you think those are materially different, then you, too, may be a hell-bound Manichean.
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You can read my more impromptu stuff at Micro.blog (mirrored at microblog.intellectualoid.com) and, as of February 20, 2019, at blot.im. Both should work in your RSS aggregator, like Feedly, should you want to make a habit of it.