1)
Why does he say that he hates Musar?
1.
Lev Eliyahu (Shemos p.160): After death, he realizes that hating Musar caused him to scream about (sorely regret) his deeds (11).
2)
What is the difference between Musar and Tochachah?
1.
Malbim: Musar is via beating or fear of punishment - this you totally hated. Tochachah is arguing with him to return him to the good path via intellectual proofs. I did not hate this, but my heart despised it; it was disgraced in my eyes.
