Abandoning abusive speech, he abstains from abusive speech.
He speaks words that are soothing to the ear, that are affectionate, that go to the heart, that are polite, appealing & pleasing to people at large.*
Of the four types of unwholesome speech, the category of abusive speech strikes me as the one most subject to self-centered manipulation. Such manipulation occurs not through abusive words, but through seemingly affectionate words.
The most soothing, polite words can be wholly false to the situation at hand. The most appealing, pleasing words can be abusive, if they obscure reality.
Indeed, falsely sweet words may constitute one of the most dangerous abuses of human trust.
Still, the Buddha counsels us to speak words "that go to the heart." Such words, in my experience, respond to and sustain the responsibility required by the circumstances of each moment.
Of course, such words aim at the transformation of heart/mind. And - here's what interests me - transformation can never be bound by courtesy and acceptability.
The Zen tradition certainly emphasizes the importance of transformational speech. Here's an example of harsh, yet non-abusive, speech, from the Tang Dynasty:
One day Yun-men went to visit Zen Master Muzhou, knocking on the gate.
Muzhou opened the gate and asked, “Who are you? Why do you come here?”
Yun-men answered, “I want to understand the original nature of life and death.”
Before Yun-men finished speaking, Muzhou grabbed him and roared, “WHAT IS THIS? WHAT IS THIS? WHAT IS THIS?”
Yun-men could not answer and Muzhou flung him back through the gate, shouting, “You’re a shit bag.”
Yun-men was despondent and ashamed. He began to practice with such eagerness that he forgot to eat and sleep. After a while he felt he understood thoroughly and was full of confidence.
So, he once again went to visit Muzhou. When he arrived he knocked again. Muzhou opened the gate and shouted, “You’ve come again, you shit bag!”
When Yun-men faced Muzhou his mind closed in confusion so Muzhou again drove him away.
Yun-men felt dejected and once again he sat without eating or sleeping. After a while he felt he understood himself and was confident.
So he returned to Muzhou’s temple and knocked on the gate. Muzhou grabbed Yun-men and shouted, “You lousy shit bag! Why do you come? Tell me! Tell me!” Again, this wiped away all Yun-men’s confidence and understanding.
Muzhou shoved him out and closed the gate on Yun-men’s foot. A flash of hot pain pierced through Yun-men’s body and his mind opened.
Yun-men shouted at Muzhou, “You’re a thief!”
At this Muzhou said, “Oh! The shit bag talks. Come in!”
Yun-men went on to become one of the greatest of masters, enlightening many students. Sometimes a bag of shit can become the world's best fertilizer.
May each of us encounter such loving abuse!