Many say that, additionally, we have to consider the culture. There was a book written before Hitler's time, but apparently when he was a teen, which had a profound effect on him and the culture in Germany. You can read some about it here.
Alfred Hoche and Karl Binding wrote "Permitting the Destruction of Life not Worthy of Life".
Another interesting thought I have been mulling is the idea of attachment. Attachment theory is about infants and children trusting their parents. We studied it in depth and saw an attachment counselor for several years after the first adoption to our family of an older child with severe attachment issues. But what I recall from the early work done on attachment is that it was highly biased by culture, and guess which country stood out in the studies, time after time? Germany. Apparently in Germany they favor autonomy so highly that they tend to push their young ones toward it at much earlier ages than most other cultures, discouraging reliance on parents emotionally, etc.
The last cultural influence that seems to boost euthanasia in countries is that of limited resources.
So if you put a strong favoring of autonomy, with limited resources, and add in a medical profession which has been geared toward eugenics thinking by a very popular book, bingo. I wonder if that gives us some avenues to fight back, besides the most effective, prayer.
I will check out all of your links over the next few days.