San Francisco’s Union Square, the high-end shopping district at the center of the city, is boarding up for the Christmas shopping season after a string of “mass looting” events that began on the weekend before Thanksgiving. Normally, Union Square is festive and bright in December. Its giant Christmas tree and menorah attract visitors from across the region, as does its outdoor ice skating rink. Situated alongside the city’s famous cable car, it is an oasis of prosperity in a gritty downtown. However, this year is different, as the San Francisco Chronicle reports: As San Francisco approached the critical December shopping...