One of the great ironies of history is that the Jews held captive in Babylon were amongst the FIRST beneficiaries of a religious system that was the World's first to prohibit slavery: the Zoroasterians (under their God, Ahuru Mazda) held this as central to their beliefs, and since it was accepted as the official State religion of the Persian Empire under Cyrus the Great, who released the Jews from captivity and allowed them to return to Judea (only to ironically pick up the practice of slavery AFTER the Greeks defeated the Persians, some 200 yrs later; they "returned to their own vomit" of practicing slavery once they got a chance). Heck, the OT even records the event in Daniel, etc.
The jews felt they were superior because their holy book told them so. They felt that other peoples were not the brothers, but labour to be taken. Just look at the book of Joshua it tells them this. Their entire religion is based on separatism and racism. Its particularly interesting that nobody mentions more than half of the jews in Babylon did not return Judea. I think Ezra gives us the supposed exact numbers. Sounds to me like many jews didnt want to return tot he old despot ways of their kings and preferred the relative better life under the Persians.