The “effective use of social media” by Islamic extremists poses new and serious threats to the U.S. homeland, but “it’s important to remember that a lot of the counter-narrative needs to come from within the community,” Homeland Security Secretary Jeh Johnson told ABC’s “This Week” on Sunday. “And so, when I meet with community leaders, I am asking them, what are we doing to counter this narrative? It is slick. It is effective,” Johnson said, referring to the terrorists' Internet recruitment. “But we need to get the message out, and that’s not necessarily a government objective, a government mission. It...