You’ve probably never heard of Brandon Darby. The former community organizer who saved American lives by undermining a left-wing terrorist plot at the 2008 Republican convention used to be a proud member of the radical left. He called for the overthrow of the U.S. government. He hated cops. He consorted with eco-terrorist tree-spikers, radical feminists and black nationalists. He was approached to rob an armored car and asked to commit arson to fight gentrification. He mouthed politically correct slogans about the Bush administration. Government didn’t care about people, and he thought the botched response to Katrina proved it. When he...