Last Saturday, for the second time in a month, protesters who identified themselves as members of the Black Lives Matter movement leapt onstage to interrupt a speech by Democratic presidential candidate Bernie Sanders. “I was going to tell Bernie how racist this city is, even with all of these progressives, but you’ve already done that for me,” said Marissa Johnson, who was roundly booed before demanding and receiving a four-minute moment of silence for the death of Michael Brown, as Sanders stood behind her and fellow protester Mara Willaford. The Seattle protest sparked a particularly strong counter-reaction, especially among the...