By Kevin Roose Oct. 28, 2018 Early Saturday, moments before the police say he barged into a Pittsburgh synagogue and opened fire, Robert Bowers’s anti-Semitic rage finally boiled over as he posted one last message online. But he did not turn to Facebook or Twitter. Instead, the man accused of killing 11 people went to Gab, a two-year-old social network that bills itself as a “free speech” alternative to those platforms, and that has become a haven for white nationalists, neo-Nazis and other...