What happened a lot at the beginning of WWII was that people didn't know what was happening at the concentration camps. And yes, there were some twisted moral templates at the time based on racism and dehumanization.
Oof, how I wish that were true. You may be interested in Pernick, Martin (1999): The Black Stork: Eugenics and the Death of "Defective" Babies in American Medicine and Motion Pictures since 1915.
Several nations (the US included) were well on their way to "Great Society" ideas of shaping the next generation by controlling genetics (be that in who reproduced or who was allowed to live). A lot of experiments ended abruptly when the Allies reached the camps, and a lot of politically-powerful institutions have kicked dirt over their own pasts to try and help people forget that's where we were headed.
(Quite a few experiments did not; forced sterilization wasn't outlawed in the US until, IIRC, the eighties).
It's because of the holocaust that we thankfully have changed our collective attitude about such things. But in 1939, people's knowledge of the racial atrocities happening was very restricted, so I don't think we can underrate just how naïve some people where at the time.