You're basically correct except for the facts. Werner did not start his career as a Nazi, he joined later, and he did not work on weapons that killed many (not countless, they did count) Brits until much later. I know that Nazi Germany lost and thus history is skewed to favor the winner's view point but after 70+ years maybe the truth will be acceptable.
Perhaps this would be more correct and convey the same effect:
Wernher von Braun's early career as a Nazi who helped develop the Retribution Weapon 2, aka V-2 rocket, (responsible for the deaths of 9 thousand Brits) did not prevent him from becoming an American hero.