This chapter is based on that book. Through the use of derogatory language, many people have been and still are viewed as sub-human. Because they diminish the humanity of the other and makes them easier to hate. The language creates an environment for lynching and genocides. By saying that abortion equals murder, pro-lifers caused the murder of several abortion doctors.
Words can kill.
In Shakespeare's Othello, the villain Iago vows to destroy the Moorish general Othello for bypassing him for promotion. Iago repeats charges often enough that Othello's new wife Desdemona is having an affair, that Othello, prone to jealousy, believes him and murders his wife, only to learn moments later that Iago's words were false. Even if you say the truth, it does not justify unnecessarily passing on hurtful information about someone. Remember, it's gossip when true, slander when false. Both are wrong.