On Saturday, Chuck C. Johnson invited his Twitter followers to send some money his way so that he could focus on his latest project: “taking out” the civil rights activist DeRay Mckesson. Johnson is a 26-year-old California man who has been described as “Twitter’s most infamous right-wing troll” (Mother Jones), a “digital Darth Vader” (Politico), “your least favorite person” (the Washington Post), and “mood slime” (the New York Times). He is best known for outing the subject at the center of the discredited Rolling Stone UVA story, publishing the home addresses of New York Times Ferguson reporters Julie Bosman and...