You are missing the forest for the trees. Examples of the same mentality are everywhere. Pretending that Mengele was unique or special will only cause you to ignore him when he wears a different shirt than you are used to, or speaks a different language. The most brutal and heartless killers are small children. You will never stop humans from enjoying killing. All you can do is give them some morality. Mengele had his morality. It came in second.
15 police officers killed in Colombia helicopter crash (Reuters)
from the article: In his diary, Mengele predicted 90% of humans would die of stupidity