How is "Ma'aneh Rach Tashiv Chemah"?
R. Yonah: [The author] begins with the gate of the tongue. He warns to accustom one's tongue to answer softly 1 . He shows the opposite about an answer with anger. A soft answer repels the anger of one who is angry at him.
Orchos Tzadikim (Sha'ar ha'Shetikah DH v'Lif'amim): If one sees another transgress, he should protest and rebuke him 2 .
Malbim: Chemah is stored in the heart; the fire burns. Af is external anger; it is revealed. When there is no Chemah with it, it is not so cruel, like a father who hits his son with Af, and in his heart he loves him. A soft answer turns away even Chemah, and the enemy becomes a lover.
What is the meaning of "u'Dvar Etzev Ya'aleh Af"?
R. Yonah: One who speaks angrily when arguing, he arouses anger.
Malbim: One who answers to pain the one who spoke to him, not only does it not turn away Chemah. It even arouses Af, to immediately take vengeance - "v'Af Elokim Alah Vahem va'Yaharog b'Mishmaneihem" (Tehilim 78:31).