At the least? Who are you, or any of us to judge which sins are greater? And for the record, I do not believe I ever said that you were going to burn in hell and I apologized for the words and actions of others.
The grandson was not innocent. God's punishment for any man is just because all men are sinful. Although you may think in the scenario with Noah that his grandson was innocent, it does not mean he is innocent of sin as a whole.
All of mankind is sinful, including Noah. He is the tip of the iceberg as far as sinful people who God has used. Add to the list David, Solomon, Jacob, Paul, etc. etc.