Sweden, seen by many American progressives as the model of multiculturalism and tolerance, has erupted into an orgy of violence as gangs of rioting immigrants took to the streets for a fifth consecutive night Tuesday in Stockholm. The latest reports indicate the riots are now spreading to the country’s two other major cities – Gothenburg and Malmo. Sweden, along with Germany, make up Europe’s two most generous welfare states. They are also the most welcoming of Islamic immigrants, more than a million of which have flooded into the continent this year from Syria, Afghanistan, Iraq, Pakistan and North Africa. The...