You can find the "limited omniscience" thesis here http://www.polkinghorne.org/, in the FAQ section

The website appears to be run by an acolyte of Polkinghorne's, and the philosphical and logical contortions in some of the answers are remarkable - but they do give a good insight into the reasoning processes of some of the more intelligent christiansYou will note that in the view of this person, we atheists are animals - not just in the biological sense, one gathers, but in a pejorative way.

If I may venture it, may I suggest that the definition of right and wrong is inevitably conditioned by the civilisation, society, and community in which we live. I would think it wrong, for instance, to force my child into a marriage he or she didn't want. In other cultures, this is quite "right", and not always or even usually for religious reasons. (Sometimes it's to settle a feud, others to increase family wealth)

A basic ethic of not willingly harming others who themselves are doing no harm seems to me to be a good basis upon which to build a system of ethics and morals.

I agree with you that the specifics of what is right and what is wrong will vary within societies. However, I believe that the process for deciding what is right and wrong should be independent of society, even if it includes reference to the prevailing morality of the society in which it is being applied. For an overly simplistic example, one might say that it is immoral to eat dogs in a society in which dogs are treated as companion animals.

What bugs me is when people say that they define "good" in terms of a deity, and then by their words and deeds demonstrate that they obviously have a definition of "good" that has nothing to do with their religion. This leads to semi-meaningless statements like, "Good is obeying God, and God would never ask you to do anything bad."

It also makes me frustrated when people define "good" in terms of the ten commandments, and then can't define them for me (e.g., what does "Thou shalt not kill" entail?)

I agree with you about not harming others who are themselves doing no harm. The only sticky point here is defining "harm." For example, I once was told by an atheist that banishment from a religious community didn't harm the banished since the religion was false in the first place and taking away something that doesn't exist isn't harmful. Since, to the banished person, the religion (and the community that went along with it) was real, I would define this as harm. This is why in addition to not harming others I would add that people should in general be treated as they would like to be treated. That's still over simplistic, but it's another step in the right direction.