First of all, Rand was a naturalist, but not a materialist. A materialist is only one form of naturalism Ė one that reduces human nature to mechanical determinism. Modern religious conservatives implicitly rule out Aristotle when they equate all secularism with materialism. It is on this basis that they create a huge gap between Objectivism and conservatism.
There are two main ways of finding Godís role in manís ethics. The first claims that God stipulates right and wrong. Without Godís stipulations there are no other grounds for ethical judgment whatsoever. If tomorrow, God decreed that killing your mother was right, it would become so, period. The existentialists (and most modern secular skeptics) agree with this viewpoint when they point out that they are anguished the God doesnít exist and tell us what to do.
The second viewpoint holds that God created our nature; human nature and our survival imply ethical principles. This can result in the same ethical basis as Objectivism except for the cosmological footnote: and God is the cause of it all. Thus, such a theologian can claim that on principle there is no breach between religion and reason. Reason just figures out the principles of nature Ė a nature that God created long ago. Most intellectual leaders among our founding fathers took this viewpoint or some similar variation. Objectivists have common ground with this religious camp especially if they hold that ethics (and consequently politics) is implicit in our nature and can be debated and established by reason. I believed Rand indicated that she accepted alliances with the religious if their public life adhered to reason and reality (I canít remember the reference right now, can anyone else?).
Neil, from your article you show that Chambers and Robins, like most conservative intellectuals, hold the first viewpoint. This makes them rather uninteresting. However, itís not clear when it comes to the other critics (i.e. Ryan and McGrath) whether they reject naturalism or see religion as a completion of naturalism. The latter would be a more interesting viewpoint. Can you say a little more about their ideas?