Why does it say "Hovishu"?
Rashi citing Targum Yonasan: They should have been ashamed. Also refer to 8:12:1:1.
Radak: Were they ashamed when they did abominations?!
Malbim: They did not feel shame by themselves [to put to heart to repent]
Why does it say "Gam Bosh Lo Yevoshu"?
Rashi: Refer to 8:12:2:1.
What is the meaning of "Hachlim Lo Yada'u"?
Radak: They did not sense shame, that someone would shame them for their evil deeds.
Malbim: Even if others shamed them, they did not know that this is shame.
Why does it say "Yiplu va'Noflim"?
Radak: The false Nevi'im and Kohanei ha'Ba'al will fall when the others in Yisrael fall, when their sin is visited on them. This is the day of Churban of the Bayis and the city.
Malbim: If two are walking and one slips and falls, through this the other will be careful not to go there, lest also he fall. If the other is blind, he will fall on the body of the first who fell, even if what made him slip was removed. So too, these who do not hear Musar and are not careful via these who fell in this slippery path, they will fall on the fallen bodies (the Nevi'im will be punished, since the nation fell via them).