"Thou Shalt Not Kill" was not a product of an abundant, decadent society, and I promise you that Neumann had heard of it.
I agree that Neumann gave humanity great scientific and technological gifts that brought us into the modern era, but so did Wernher von Braun. Both also used their gifts to cause suffering and destruction on a massive scale.
We can't just whitewash their history; given their intelligence we must admit that they knew what they were doing and what they were angling for. And it still matters, because very intelligent and clever people in today's world are building weapons and killing machines, and hiding behind the same excuses.