@nicolaou
Let's
make the assumption as many Christians do that the Bible is historically
accurate. The Noachian flood actually happened a little less than 4,500 years
ago after which eight adults stepped off the ark to repopulate the planet.
That
means that approximately 60 million lives had been snuffed out, a holocaust by
anyone's estimation. As if that isn't horrific enough just think about the
babies, toddlers and young children God killed.
***
The only connection I see with the flood and the holocaust (rather: I am forced to use your comparison...) is that the flood of the world removed the perpetrators of the holocaust not the victims. The flood of the world swept away the then "Mengele" with his pseudo-medical experiments on humans. If there were "unclean" animals in the time before the Flood, then the question is what all that society was doing for animal and human experimentation... what experiments on children it was committing, what disgusting bestialities it was committing...
Nobody feels sorry for the perpetrators of the Holocaust. No one feels sorry for the Japanese doctors who experimented on people, no one feels sorry for the end of the German extermination camps, where people went straight from the freight trains to their deaths by suffocation... it doesn't matter if there were 15, 20 or a million Mengele. They created conditions that were unbearable for life and lost all humanity.
The flood was survivable, and it was survivable because people were warned. Only Noah and his family took it seriously.