after 1946 ... late 1940s ... immediate postwar period. These sources contradict your claim, and suggest that both America and Australia were disgracefully antisemitic when Oppenheimer wrote his letter.
I'm not really disagreeing with you, just pointing out that by the late 1940s attitudes had changed. It seems likely that process was gradual as people learnt what had happened in Europe.
Given that Oppenheimer was Jewish himself I suspect his comments probably were more about Feynman's character compared to other physicist rather than his religious and cultural background.
