You obviously don't get it
I'm sorry, but let's get a few things straight for you. The world was very corrupt at this point in biblical times, and god drowned everyone because they had all lost faith in him and were worshipping deities and whatnot. I'd be pretty damn pissed if my worshippers (hypothetically speaking) would go around and worship little bronze statues of nothing instead of paying homage to me, their creator. Hence, they would all go to hell.
Next off, its not a sin to drink or get naked. It is a sin to worship other deities because it blashpemes against the name of the lord.
And in any case, you are far too cynical about the flood story. There are many other ways you could make fun of the bible without concentrating on the flood story, which is meant to be taken lightly anyway.
Finally, as a note, Jesus didn't come along for about another thousand or so years, so its hard to say he killed all of those people during a time when he didn't exist.