It’s a scene we’ve watched a hundred times: A public figure glares into the camera with an expression of outraged innocence and declares, “I am not a crook!” or “It was dehydration, not a drug overdose!” or “I have never had an affair!” Most of us in the viewing audience used to give these folks the benefit of the doubt, but not anymore. We’ve grown jaded watching a succession of well-known people make bold disclaimers that later proved to be flat-out falsehoods.

Of course, this always makes me conscious of my own weasel-ish tendencies. It’s so easy to commit the [...]