At around 11 p.m. on July 25, Restituto Castro received an anonymous text message asking him to leave his house in the Caloocan district of northern Manila and come to the corner of the McArthur Highway. Just hours earlier, the Philippines’ new President, 71-year-old Rodrigo Duterte, had given his inaugural State of the Nation address, in which he repeated the vow that saw him elected by a landslide in early May. “We will not stop until the last drug lord … and the last pusher have surrendered or are put either behind bars or below the ground, if they so wish,” said Duterte. Castro, 46 and a father of four, was neither a drug lord nor a pusher. He never even bought...