One word for this is "tradition". If I've piqued your interest, please read Alasdair MacIntyre's book "After Virtue," and also it's sequel with a more provocative title, "Whose Justice? Which Rationality?"
The mere presence of debate does not preclude certainty about overarching principles. Various denominations might disagree about what's moral in a situation, but they can at least agree about why this specific kind of morality is important, and what reasoning and evidence should be relevant in the discussion, and how this morality plays into a larger conception of the Christian life. Elements like the Gospel, the Apostle's Creed, and the metaphysics of traditional deism can all be harnessed to conduct and resolve debate. There are more certainties than there are the opposite. And perfect certainty will never be achieved, even on a theological level. Since one of the charges of theology is to adapt and present Christianity to a changing world.
Unlike, say, secular moral discourse, especially manifest in political speech, which makes no effort whatsoever to establish shared principles. There are few, if any, first premises which can initiate debate. There are few agreed-upon standards for what counts as relevant evidence, or how certain values outweigh others.
Wading in secular moral philosophy, the situation becomes even more dire. No one could ever hope to walk into a secular philosophy class with modern material and achieve any guidance about how to conduct their life.
The ability to debate and resolve issues is the marker of a healthy tradition. Not all issues can be resolved. But there should at least be a vehicle to coming to the best available answer. Studying, say, the progression of Catholic theological doctrine is a good example of this. But in our post-Reformation era, in which every theological debate ends up spawning a new Protestant denomination, your lack of confidence is understandable.
I do, of course, agree with you that our broader cultural approach to such issues is entirely arbitrary and resistant to intellectual progress.
Edit: Alasdair MacIntyre's Whose Justice, Which Rationality is a stellar treatment of this problem you're noticing:
http://www.amazon.com/Whose-Justice-Rationality-Alasdair-Mac...
http://www.amazon.com/Whose-Justice-Rationality-Alasdair-Mac...
I do agree that it seems very weird to call Rorty "largely forgotten".
(One pair of data points, from the person whose knowledge of such things I know best, namely myself. I am not a philosopher in any sense beyond that of having a bunch of books on philosophy. If you asked me out of the blue to name a book by MacIntyre, I would definitely remember "After Virtue", might remember "Whose Justice? Which Rationality?", and would not be able to think of any more. I could give you a crappy one-or-two-sentence summary of what AV is about (which would e.g. largely fail to distinguish his ideas about ethics from Anscombe's) but couldn't tell you much more about his work. If you asked me out of the blue to name a book by Rorty, I probably wouldn't be able to but would probably recognize a couple of his. I could tell you I thought he did important work in the general area of epistemology but not more than that. So to me MacIntyre is a bit more famous than Rorty. But my sense is that that's a bit unrepresentative among not-really-philosophers, and probably quite a lot unrepresentative among actual philosophers.)
"[T]he contemporary debate within modern political systems are almost exclusively between conservative liberals, liberal liberals, and radical liberals. There is little place in such political systems for the criticism of the system itself, that is, for putting liberalism in question" (Alasdair MacIntyre, Whose Justice? Which Rationality?, 394).
Smugness is a problem for liberal liberals and conservative liberals alike. Perhaps smugness is a natural temptation or outgrowth of liberalism itself.
