Decades before social media and email a remarkable but unsung Bronx housewife named Ruth Goldstock told her grandson, “Never put anything in writing that you wouldn’t want on the front page of the New York Times.” These days, that wise advice applies to private communications by everybody in the entire country except elite journalists and news executives. Elsewhere in America, when emails that the author assumed would never see the light of day became public he suffers some form of consequences—you know, stuff like plummeting poll numbers, possible jail time or forced resignation. This goes for everybody from Hillary Clinton and...