There are political, scientific and military issues here.

Von Braun would seem to have been at least as culpable as Albert Speer, who was tried and convicted as a war criminal. That would make von Braun a war criminal.

However, Speer's particular talents weren't needed in any post-war regime, so he headed off to the slam.

The political considerations overrode the law in von Braun's case, and he was whitewashed in American public opinion so as to make way for him. The propaganda campaign on behalf of the guy was extensive.

A - He was a war criminal.
B - The US wanted him. So,
C - He wasn't tried, even though he would have been convicted.

Arf (and they say there is no moral relativity)