Did God understand what he was getting into when he created humanity? I mean, why would an all-knowing perfectly good God create a species who he knows he's going to be condemning a certain percentage of it?
Is it possible that God in fact did not know what he was unleashing when he gave humanity free will and that God only knows the future when he directly intercedes? Maybe Genesis 6:5-7 is to say that the future could have turned out differently and that God did not actually see that mankind would be so evil as to be deserving of a calamity?
Now as it is, I am a believer, but there's of course still questions that need to be hammered into answers.