When Qatar was accused of sponsoring jihadi violence, people around the world drew back instinctively. To charge a country with backing terrorism is the geopolitical equivalent of charging an individual with child abuse. The accusation is so monstrous that, somehow, the presumption of innocence gets reversed.

Behavioral psychologists say that, when we are presented with an assertion, we tend to believe it in the absence of contrary evidence. Sure enough, there was an initial willingness to go along with the anti-Qatar coalition of Saudi Arabia, Bahrain, the United Arab Emirates, and Egypt. Donald Trump accepted their version of events unhesitatingly, tweeting that their blockade would be “the beginning of the end to the horror of terrorism!”