That's not what is being discussed here -- what's in point are his wonderful mathematical prowess, not his principles. Being good at one thing doesn't imply pristine ethics.

You also have to remember that those figures have pretty much all they ever said scrutinized, so that tends to distort things -- I'm pretty sure everyone one time or another made some unethical remarks, specially as a WWII fugitive. Horrible things happened in Europe and after that the harshness of Stalinism was also clear. I think it wouldn't be hard to get caught in "ultra-Americanism" at the time.