The Fusion GPS news-for-hire scandal has not only led to the public identification of the source of the “Trump Dossier”—a for-profit company that provides opposition research to whoever could write big checks, which is staffed by four former Wall Street Journal reporters led by Glenn Simpson. The scandal has also lifted the lid off a sewer of corporate information warfare and opposition research that the flailing institutions of the mainstream press now regularly re-package as news, without ever saying where it came from—or who paid for it. While the idea that the products of paid opposition research are being main-lined...