I believe that their Eastern European cultural memory reflexively equates a devout "Christian" with the East European "Christian" (in the loose sense of the word) mobs that devastated Jewish communities in Czarist Russia and Poland in the 19th and early 20th Century pogroms.
Their cultural and ancestral memory equates a non-secular "Christian" with :
These pogroms were not only tolerated but sometimes even encouraged by Czarist authorities.
It is no wonder then that Eastern European Jews were such a large component of the early Communist movement. In theory at least, Communism offered the overthrow of the hated Czarist regime, the destruction of the "Christian" religion whose clerics encouraged the pogroms and the establishment of a secular state with complete equality for Jews.
Of course, theory and practice are two different things. Over 90% of the Jews who fled the Czarist Russian pogroms ended up in the United States. Most of those came before the birth of the Soviet Union. They never saw the evils of the Communist system first hand.
So, the ancestral mind set becomes:
Czar = Bad.
Communism = Enemy of the Czar = Good.
Christians who take religion seriously = Pogroms = Dead Jews = Really Bad.
Secularism = No Christians = No Pogroms = Really Good.
Of course, the 21st Century American Bible Belt Protestant, who doesn't know a pogrom from a pierogi, is a totally dofferent animal from the 19th Century Russian "Christian" peasant burning down great-garndpa's village. However, the ancestral memory A.) Does not realize that or B.) Doesn't want to take any chances.
This, of course, does not apply to all American Jews as Yaelle pointed out.
Growing up Cuban American in Miami, I was exposed to quite a bit of Judaism. Our "Jewban" fellow Cubans hated Communism just as much as we Catholic Cubans did, were just as Conservative as we were and weren't threatened by our Catholicism.
Later on, while studying the history of our ancestral Spain, I became interested in the Sefardi Jewish diaspora into the Mediterranean. (I even learned Ladino, Yaelle. :-) See Post 58.)
The Sefardi, didn't have the Left-wing mind set and the Sefardi that came to America before the great Ashkenzi immigrations of the late 19th Century felt no threat from American Christianty.
So, there must be something else about the Ashkenazi that was different. It wasn't only Judasism that made them think the way they did. So, from my historical studies, I came up with my ancestral memory theory.
Now, the question I have for Yaelle is: What was it in your own particular Ashkenazi background that made you march to a different drummer and make you a Conservative?