"I think Mengele’s case highlights how the idealised image of the objective Academic, struggling only to further knowledge, can be a road straight to hell."
A quote from this post on the Phineas Gage Fan Club blog. It's a grand post, I highly recommend reading it. The author considers Mengele as model of villainy and evil. There is an interesting thought here. Mengele wasn't one-dimensional. He was not pure evil, although he did some terribly evil things. Many speak of him having a playful side. Hitler, I have read, was very cordial in person and had a great sense of humour. The holocaust is an example in many ways of pronounced faults in human psychology that we must all be personally aware of and careful about. The author in the aforementioned post mentions the danger of logic without controls. Logic is a tool. It is an extremely valuable tool, but if it is not regulated by morality and ethics it can lead in bad directions.
We can see this when we consider the behaviour of individuals in the Enron scandal, or even spammers. The behaviour they took part in is to a person in their position completely logical and reasonable. This is evaluating the situation without the benefit of ethics. Pure logic can be very destructive without an ethical framework within which it can be contained.