Christians, what did people have to do to deserve the Noahtion flood?

If you look at the past century, war, revolutions, and genocide racked up a body count in the hundreds of millions. This included everything from castrating children to freezing men while pouring boiling water down their throats. I don't imagine cavemen 6000 years ago even had the capacity to come up with acts this depraved, and I am convinced that there are more evil people in this world today than there were people, evil or good, 6000 years ago. I guess the question is, when do you expect god to do something about it, like he does in the bible? Isn't his absence slightly odd?