Noah’s behavior (Gen 9:20-21) is treated as quite shameful. Why?

First, getting quite drunk is portrayed as sinful, or at least very foolish, in a number of places. For example: “Wine is a mocker, strong drink is raging: and whosoever is deceived thereby is not wise.” (Prov 20:1) But while nakedness is itself is no sin, public exposure (even being “uncovered within his tent”) is treated as shameful in the Mosaic code. (And throughout, we must remember that the author of Genesis was the author of the Mosaic code; and that God was the real author throughout.) Noah’s nakedness while drunk raises the question why he was naked; there may be some implication of sexual impropriety; see next question.