Based on history books I read (mostly from Richard Evans), they knew. Nazi violence and concentration camps were public knowledge, because the regime needed to generate the fear. Germans prior war were in fact scared a lot.

This particular book is a out what nazi sympatizants and nazi themselves were saying after the war. It is what it is, but there was real motivation to not have own culpability in destruction of Germany in the open. (Which is what they have seen as tradegy, not the holocaust itself all that much)