In normal times, the televisions are humming at the FBI’s 56 field offices nationwide, piping in the latest news as agents work their investigations. But these days, some agents say, the TVs are often off to avoid the crush of bad stories about the FBI itself. The bureau, which is used to making headlines for nabbing crooks, has been grabbing the spotlight for unwanted reasons: fired leaders, texts between lovers and, most of all, attacks by President Trump. “I don’t care what channel it’s on,” says Tom O’Connor, a veteran investigator in Washington who leads the FBI Agents Association. “All...