Marcy Wheeler’s decision to out her source to the FBI
Margaret Sullivan writes: It’s pretty much an inviolable rule of journalism: Protect your sources. Reporters have gone to jail to keep that covenant. But Marcy Wheeler, who writes a well-regarded national security blog, not only revealed a source — she did so to the FBI, eventually becoming a witness in special counsel Robert S. Mueller III’s investigation of President Trump’s possible connections to Russia. “On its face, I broke one of the cardinal rules of journalism, but what he was…