A new book, "An Ugly Truth: Inside Facebook's Battle for Domination," details how Facebook struggles and sometimes fails to curtail hate speech, disinformation and violent rhetoric on its platform. It also examines how Facebook has become an enormously lucrative data mining and advertising operation. Authors Cecilia Kang and Sheera Frenkel join William Brangham with more. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders