YouTube is designed to catch you and not let go. Sometimes I access the site just to watch one thing, but then one of the related videos catches my eye. I watch that one, then another and another, and soon a five-minute visit has stretched far longer. If it’s half an hour of movie trailers, then I’m just indulging in a guilty pleasure. But what if I followed a link to “Q—The Plan to Save the World” and wound up staying for one outlandish conspiracy video after another? YouTube’s associative linking is designed to keep me clicking and watching. It has turned into a mechanism for political indoctrination, suggesting through sheer repetition that an international cabal is threatening to take over the world.