Oppenheimer was a windy gasbag too.
Nuclear research, despite being weaponized, gave the world a lot of good things too: X-rays, MRI, cancer treatments, etc.
Nuclear war, horrible though it would be, would not end life on earth. See: Chernobyl where plant and animal life thrives and is overwhelmingly without genetic defects.
Nuclear war is a contradiction in terms to say the least. No one has ever fought one. Dropping two atomic bombs on two undefended cities can hardly be called nuclear combat. And Chernobyl , though caused by an over heated reactor core was more of an accident than something done deliberately.