That I'm not entirely sure about. Perhaps it has something to do with Stalin's regime, or perhaps it's that atheism, socialsim, and communism are seen as anti-American, causing people to automatically link them together.
Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own - Bertrand Russell