Because harsh words disturb others’ minds and cause the Bodhisattva’s conduct to deteriorate, abandoning harsh speech which is unpleasant to others is the Bodhisattvas’ practice.
A bodhisattva’s practice is to rid ourselves of harsh language
Displeasing to the minds of others,
Because harsh words disturb others’ minds
And cause our bodhisattva ways of behavior to decline.
– The Berzin Archives Thirty-seven Bodhisattva Practices
(Bodhisattva — In Tibetan Buddhism, a Bodhisattva is anyone who is motivated by compassion and seeks enlightenment not only for him/herself but also for everyone…)