Can you site your references please. I'm not aware of any Nazi "scientists" that conducted eugenics experiments not being prosecuted. Who are you referring too (or did you just make that up?).
There were German scientists that developed rockets and other advanced technology that were employed by both the East and West in the in Cold War.
Found some stuff on it it. http://www.operationpaperclip.info/kurt-blome.php
Operation Paperclip. Specifically Kurt Blome. He did get nabbed by French Authorities way down the line after the US made use of him.
Looking at the bottom of the page worries me though. Says Content modified from Wikipedia...Don't really like that...seems credible though. Will attempt to crosscheck the sources and see if I can find a more credible site.
It seems it is more a case of they likely took in whoever they could and some of the scientists conducted eugenic experiments but there is little evidence for it that is unclassified. Of course it could all be BS anyways. Maybe the US really did only take in Nazi scientists who did not experiment with eugenics. They never game real pardons though.
Edit: It appears I was somewhat ninja'd.