Hi Duster,
Thanks for your post. The presenting of Prophets, including the Prophet Muhammad, as perfect or near perfect human beings from what I understand is somewhat of a later Islamic tradition. I say "somewhat" as the Qur'an, in preaching a message of repentance to Arabs, does not elaborate on the failings of the Prophets, but focus' on their obedience to preach repentance.
However throughout the Bible, it presents the life story of the prophets, this is different to the Quran. It presents the "Good, the Bad and the Ugly" of Prophets, that even they are fallen human beings, sometimes in a major sin, and throughout, genuine repentance brings them back to God. This is evident through the Psalms, which are often songs from the heart of David crying for mercy.
Therefore the purpose is not to promote sinful acts, but to emphasize mans sinfulness and Gods mercy. The specific instances you mention have a context.... In regards to Noah's nakedness...(Genesis 9) Shem's brothers are presented as the "villians", and Shem as the positive example. There is no indication in the text of homosexuality... that is a massive "reading into the text something that is not there." However Shem's brothers are disciplined for exposing and gossiping on another's error, whilst Shem is held as an example as he gave dignity to another, even though there was a problem, and didn't judge another for it, but instead was compassionate.
About Lots children, again it is not condoning the actions, but the context was they were some of the last of their people, distraught, and made it mistake...
A part of this is for people not to read the Quran as if its the BIble, and not to read the Bible as if it is the Quran. Hope this helps...
Wasalam
Zack