It is pretty difficult to understand but it happens in stages. Your average German could claim to not have known about the gas chambers but they knew the Jews were rounded up in ghettos. Then rounded up and removed. And never seen again. And they heard the rhetoric..... many would have heard rumours of gas chambers but it is possible to think that they wouldn't have believed it.
Just one of many examples of how thin the veneer of civilisation is. And what lurks beneath it.

