BDS sufferers are overwhelmingly members of the intelligentsia, at least as self-defined: academics, "artists", and the commentariat, and related wannabees. They have in common membership in a subculture that is, geographically, largely confined to cities and the Northeast, and tends strongly to be passed down in families.
George W. Bush had every opportunity to become one of them. His father is a member in good standing of that culture; his mother is a Pierce. Absent malign influences, a reasonable person could have looked at young George and predicted that he would grow up to be, for all practical purposes, John Kerry.
Instead he went off and actually joined the "red staters", complete with religiosity and drawl. Apostasy always causes heartburn in the Faithful -- the fear that, if it happened to him, it could happen to them or their descendants, too. How could such a thing happen? Shun him! Shun him!
This reinforces the evidence that Leftism is for all practical purposes a religion.