How do false lips cover hatred?
Rashi: A flatterer, his lips [speak] Sheker and cover hatred in his heart. R. Yonah - "b'Fiv Shalom Es Re'ehu Yedaber uv'Kirbo Yasim Arbo" (Yirmeyah 9:7). The verse comes to debase the Midah of hiding hatred.
What is "Motzi Dibah"?
Rashi: It is detriment that people speak about someone.
R. Yonah: It is one who verbalizes all his Ru'ach. If he seeks or thinks bad about his hater, he says it.
Why is "Motzi Dibah" taught after covering hatred?
R. Yonah: One should not say, it is good to reveal everything in his heart about his colleague, both hatred and Dibah. A hater should reveal hatred in his heart, but not Dibah. The Torah explained how to deal with hatred and Dibah - "Lo Sisna Es Achicha bi'Lvavecha Hoche'ach Tochi'ach Es Amisecha v'Lo Sisa Alav Chet" (Vayikra 19:17). Do not bear sin via rebuking him in public and making him blush; rather, rebuke him when no one else is there.
Malbim: There are many evils in "Motzi Dibah." Surely he will hide his hatred, in order that people will believe his slander. He is a Kesil, for he acts opposite to Chachmah due to his evil heart.