Why does Noah curse Canaan?

Question

Genesis 9:23-25 NLT, reads,

Then Shem and Japheth took a robe, held it over their shoulders, and backed into the tent to cover their father. As they did this, they looked the other way so they would not see him naked. When Noah woke up from his stupor, he learned what Ham, his youngest son, had done. Then he cursed Canaan, the son of Ham: “May Canaan be cursed! May he be the lowest of servants to his relatives.”

He couldn't be that bashful. What's going on here?

Answer 1

On why Canaan and not Cham, I asked on J.SE and among the possibilities suggested in this answer is that God had already blessed Noach's sons and you can't counter a blessing with a curse. So even if Noach had intended to curse Cham, he couldn't and went for his son instead.

(There are other opinions there too, but that's the only one so far that comes clearly from a straight reading of the text without extra sources that might not be as accepted on BH.SE.)

Answer 2

Well modesty does mean much more in the Bible than what it means in our modern culture, but the best view I've seen is the maternal incest idea.

• "Uncover Nakedness" is used in Leviticus to describe heterosexual incest
• the "nakedness of the father" is identified with the "nakedness of your mother" (Lev 18:7-8)
• If this is about Ham's incestuous sex with his mother, the emphasis on Canaan comes clear. Canaan would have been the product of the incestuous union. That is why Canaan is cursed, and why the text consistently identifies Ham as the "father of Canaan." It is suggested that the narrative has been compressed, and that the curse was actually pronounced at Canaan's birth rather that immediately after the incest.
• This view highlights better the connection of Genesis 9 with Genesis 6, 19, Leviticus 18, 20 and Dueteronomy 23:1, 27:30, and the maternal incest of Reuben. It shows that the chief enemies of Israel - Canann, Moab and Ammon - are all of questionable heritage.
• It preserves the idea that has been brought forth that this was an attempted seizure of Noah's authority, quoting a 1971 article from FW Basset: "A son who has sexual relations with his mother or step-mother commits a rebellious act against his father, since the possession of a man's wife is seen also as an effort to supplant the man himself." Note the connection with Absalom, Reuben, David's taking of Saul's wives, and Adonijah's attempt to have Abishag.
• It was noted by Bergsma & Hahn that "the tent" in v.21 "appears to have the feminine possessive suffix" though "the MT points the word according to the qere," i.e., as "his tent". "Thus, one might read the text as saying that Noah entered "her tent," the tent of Mrs Noah.

The first link has more explanation, and is where the unattributed quotes are derived.