From combating Democrats and the liberal media as an anti-Russia hoax House chair, former California Rep. Devin Nunes is now atop former President Donald Trump’s startup social media challenge to leftist Silicon Valley. “What these companies have been getting away with is something we have never seen in the history of the globe because a lot of these tech tyrants are bigger than what global empires were in history,” Mr. Nunes told me in an interview. The first item Mr. Nunes wanted to talk about is the same message he had in Washington: Don’t believe “fake news.” In this instance,...