There's a difference between criticism and understanding. We can understand why people felt and acted the way they did in a given time period, but that doesn't mean that we need to sympathize with them or that they are somehow immune from criticism.
Individuals are not just a victim of our circumstances, and morals about the sanctity of human life are far older than the 20th century and appear in times of deep discomfort as well as times of comfort.
If you want to criticize, imho, criticize someone who actually did wrong. Those who expressed an opinion found to be a bad call almost a century in the future aren’t worth the bother in my opinion.
We were incredibly lucky to have JvN.
"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.
Let's not forget how close to war we came during the "bay of pigs" era.
Criticizing that from the comfortable perspective of today or even halfway to the sixties, doesn’t make a whole lot of sense. Also being smart apparently doesn’t help much in predicting the future.