What do you think a moral retard is?
I'd say it's a legitimate term, and not just something that the fundamentalist Right is able to throw about. Thomas Sowell describes it well in his famous quote "The problem isn't that Johnny can't read. The problem isn't even that Johnny can't think. The problem is that Johnny doesn't know what thinking is; he confuses it with feeling."
Christianity is not the only moral system capable of being compatible with the classical West. I will argue that it certainly is a useful moral system. There are a handful of tenets I disagree with, but they don't matter in day to day interactions with my fellow man. Stoicism is another that is compatible with Westernism. Rationalism is another. Or Objectivism. Even more alien and exotic philosophies and moral codes are reasonably compatible with Westernism, such as Taoism or Zen.
Honestly, most moral systems and philosophies, when explored THOROUGHLY and delved for understanding, are compatible with Westernism.
The trouble here is that children born in Western societies are not being taught ANY moral system or philosophy. The only evidence I can see of anything being taught in public schools that echoes any semblence of a moral system, is Moral Relativism mixed with a healthy dose of Presentism (judging history by today's standards). The only outcome a person can draw from that, without some other philosophical or moral buffer to filter it, is relative disgust towards your fellow man in all cases. And so we have a world that becomes ever-envious and spiteful, experiencing the world and our interactions with it through the prism of emotion rather than thought and morality.
Such is a moral retard. One who has had their moral growth retarded due to neglect or poor instruction.