Two weeks ago, many Londoners were asking whether the time had come to get off Facebook altogether. Individuals who have blithely used the platform for years were fearing for their privacy, security and politics. Yet the implications for communities are as insidious, and perhaps even more destructive, as for individuals. Victoria’s mayor, Lisa Helps, in a blog titled “Why I’m quitting Facebook,” decided the time had come for her because: “Facebook peddles in outrage . . . It has become a toxic echo chamber where people who have anything positive to say are often in defense mode against negativity and anger. Continuous reinforcement of existing beliefs tends to entrench those beliefs more deeply, while also making them more extreme and resistant to contrary facts.”…