Almost the entire population of Italy, it seems, spent the last week of June watching a boat arrive from across the Mediterranean. It was the Sea-Watch 3, a Netherlands-registered ship funded by progressive philanthropists and captained by Carola Rackete, a 31-year-old German climate-change activist. Rackete radioed that she was carrying 42 African refugees rescued at sea who were in desperate health. Italian interior minister Matteo Salvini holds that such ships rendezvous with traffickers just off the Libyan coast, and are really less interested in rescuing sailors than in transporting illegal immigrants to Europe en masse. “Taxis,” he has called them....