hamilcarr: I wouldn't agree with this. The "clear moral norm" is a reality on which our civilisation is built. Morality isn't the product of our culture and civilisation, but rather the opposite: civilisation is the result of our biologically rooted moral potential (which may be emprically confirmed by comparative behavioral studies).
There is no "clear moral norm" upon which all mankind agrees; it is, in that case, no more real than "respect". Comparative behavioral studies always show the bell curve ranges of human behavior and analysts, looking at the statistical breadth of the bell, draw an arbitrarily determined line through it and say, "Above this line is normal as it pertains to this specific aspect of comparative behavior, below is abnormal."
Who, outside their arbitrary selves, determines they are right about normalcy? It is an important question to answer because empirical proof is the stuff of hard science.
But let us put your statement to the test: "Clear moral norm" is the reality upon which our civilization is built.
Are you pro-choice or pro-life? Are only theists pro-life? Are all theists pro-life in all contexts? If not, why not?
Are you opposed to homosexuals being allowed to get married or are you in favor of it? Are only theists opposed to it? Are all theists opposed to it? If not, why not?
Side-question pertaining to the following question: Is China part of "our" civilization?
Should people be allowed to own slaves? Are all atheists opposed to it? Are all theists in favor of it? If not, why not?
Who is part of "our civilization"? Do all atheists agree? Do all theists disagree? If not, why not?
Should adults build long-term committed relationships or should the stronger evolutionary drives to multiply for special preservation be heeded? Do all atheists agree? If not, why not?
Our nation is not built upon a "clear moral norm" and our world civilization is certainly not. The United States of America has been struggling to develop moral normalcy as a direct result of its contractual civilization ever sense its founding. I say again, putting your statement to the simplest real-world challenges crumbles it to dust immediately.
Moral schmoral: morality either exists outside of humanity and is something we are all struggling toward or it only exists in our minds, and is a concept easily dispelled on simple questioning. In the former case, it is real but not our own. In the latter; it is no more real than hate, and is just as constant. In the former case there may be something stable upon which to build . . . anything. In the latter, morality is as fickle and whimsical as an individual's momentary choices.
Our "biologically rooted moral potential" has a darker conjoined sibling called "biologically rooted immoral potential". Who's to say which is which in any given instance?