Does he treat this person as a person, or merely as a servant? Kind words aren't meant only for friends. We're to offer them to everyone because they, like us, are made in God's image. You can't bless God and curse his image at the same time.
If we're going to be the kind of people who use words wisely, then we've got to first cultivate an inner life that sees everyone as a friend created in God's image.
We need a vision of life that doesn't put us at the center of the universe, but rather centers on God and God's purposes. The God who spoke the word of creation and sent the Word to become flesh in his own Son, urges us to choose the kind of words that reflect his character, life and love.