David Hogg, a 17-year-old student who survived February's mass shooting in Parkland, Florida, on Monday night downplayed claims that his boycott of Fox News host Laura Ingraham's advertisers was being led by "powerful, shadowy radical groups." Hogg appeared on MSNBC's "The Last Word," where he was asked about former Fox News host Bill O'Reilly's tweet about the boycott "being directed by powerful, shadowy radical groups who want Laura Ingraham off the air." The boycott, which has been pushed by Media Matters for America among other liberal-leaning groups, has led to at least 15 companies dropping their ads from her show...