When atheists and secular humanists dismiss Christianity, they are dismissing more than religion. They are dismissing a cogent moral system, along with the system of rights that system bestows upon us all. Lest we forget, our inalienable rights, which form the basis of our constitution, are granted (and not revocable by government) by our Creator. While they argue that they can arrive at a cogent moral system (which I have not yet seen demonstrated) they cannot arrive at inalienable rights because no such thing can exist from a secular atheist perspective.
However, I discovered another significant problem when one dismisses religion and specifically Judeo/Christian religion, how do does one arrive at the “aboutness” of what it means to be human? Let me explain. I work in the information technology industry and one of the hot topics these days is metadata or the exposed or named properties that give the “aboutness” of the information object. Someone has to make cognitive external assessments in order to analyze and assign these understandings. For Christians and Jews, our aboutness is assigned by God himself, part of which is included in our inalienable rights.
After some reflection I came to the conclusion that these two issues intersect and create a fundamental problem for atheists/agnostics, and that is, if you only have an internal frame of reference and there is no external assignation of rights and aboutness, then where does it all come from? If the rights and aboutness only come out of the internal human dialog, then they are totally subjective and malleable and cannot produce anything inalienable. Everything will be momentary and subject to change.
In the end, looking at history, we as a country, as a social and political system, only exist because our forbearers lived and moved and breathed in the ether of Christendom, with its fundamental dignity of man and God-given rights, inalienable rights that give us an essential aboutness. Atheists could not have produced that. On the contrary, as far as I can see they owe what intellectual and moral framework they have to us who created the ether in which they swim.
Update: This also has been posted on Theologica where you might want to look at the comments.