In the feverish heyday of the “birther movement,” conspiracy-hungry readers swarmed to a website called WorldNetDaily for the latest on the specious yet viral theory that President Barack Obama was not born in the United States. The site’s founder, Joseph Farah — a former newspaperman with a dense, jet-black mustache and a cloak-and-dagger mystique — boasted in 2010 that he was well on the way to generating $10 million a year in revenue. His Northern Virginia-headquartered news site, known by the acronym WND, was having its moment by stoking rumors about Obama. But Farah — a conservative Internet pioneer who’d...