Michael Moore set the record for the highest-grossing documentary of all time (1989’s “Roger & Me”). Then he broke his own record (2002’s “Bowling for Columbine”). Then he broke it again, with what remains the highest-grossing doc in US history, 2004’s “Fahrenheit 9/11.” Along the way he won an Oscar and predicted Donald Trump’s presidential victory when no one else saw it coming. That was then. These days Moore’s IRS-reported income is (according to legal papers filed by his ex-wife, Kathleen Glynn) negative-$350,862 (in 2014) and negative-$221,025 (in 2016). He’s still making movies, but America is yawning. Already there have...