You make the error of confusing “morality” with stability.
I said, for societal stability, marriage is crucial. Evolution is about throwing random combinations into a box and seeing which one survives the tests made to endure. Something will almost always survive. If that’s the goal, then yes, you can have chaotic behaviour and still survive, albeit at a non-optimal level.
With the stability of the marital unit, however, human resources are better leveraged toward managing the (seemingly) mutually contradictory goals of individual survivial and greed versus societal survival and converts them into mutually supportive goals. The stability of the marital unit allows the environment of supportive collaboration to be strengthened (the bedrock of societal existence) thus enhancing individual survival whilst also feeding back to the societal structure and reinforcing it. This is all evolutionarily favorable, and the reason why disparate societies have adopted the strategy (convergent social evolution).
Fostering fear and violence within society disrupts mutual collaboration. Justice is essential whenever punitive action is taken, in order to prevent the upsetting of societal stability - because otherwise, large sections of its comprising members will act upon the feelings of injustice and resort to destabilisation. Empathy fosters collaboration. A society that fosters elimination of its weaker sections will also foster instability by increasing insecurity. This is all a no-brainer. I’m surprised you’re asking, even:
No superstition / deity necessary to witness the logical reason for all of this.
I made no mistake: morality is necessary for stability, for reasons you list, which was not needful as the wisdom of marriage was not the issue. And i am glad you support marriage (which i presume is monogamous?).
A society that fosters elimination of its weaker sections will also foster instability by increasing insecurity.
But some will argue fostering a constant high degree of insecurity is necessary for stability, that of a controlled society, as in the atheistic Soviet Union.
This is all a no-brainer. I’m surprised you’re asking, even:
Then you did not understand my point, which which was not that an atheist cannot have solid reasons we concur with for things, but that another atheist can argue against you on such things as marriage, or support gay marriage, etc., porn, consensual sex based upon their reasoning.
Some sanction casual fornication or with a "committed" (overused and often superficial term today), even btwn kids just out of puberty. The atheist Austin Cline over at About.com Agnosticism, when not misrepresenting Christianity with the usual atheistic scorn, thinks "the current Western notion of marriage as being only between a single male and a single female is culturally and historically conditioned - there is nothing very necessary or obvious about it. Other types of marriage can be just as stable, just as productive, and just as loving. There is no reason to eliminate them from the category "marriage" except, perhaps, as a means to promote religious or cultural bigotry.
None of this means, of course, that two people in a committed and loving relationship must get married. ...Not being married is no more a barrier to having a deep and meaningful relationship than is not having religion. - http://atheism.about.com/od/atheistsweddings/a/whymarry.htm
George A. Ricker of Godless in America is even more clear in his support of gay marriage. Which i assume you oppose.
More examples on basic moral issues can be given, and without a proven transcendent moral standard to at least argue from, what you consider a no-brainer can be contrary to what seems reasonable to another atheist's brain.
Then are you arguing that stability is "good" but not "moral?" Because the traditional understanding of morality is the attempt to understand and act upon that which is good. But because "stability" is simply a byproduct of the processes of a series of random changes (aka evolution), then stability versus nonstability are arbitrary variations in the chaos. Nothing more.
But you have argued such attributes tend to promote survival. True, possibly. However, there are cases where "stability" has led to stagnation and failure to survive. So "stability" in the abstract is not an assurance of survival.
But survival itself is presumed to be "good" without rigorous proof. Why is survival good? We are most of us wired to prefer it. But that is tautology, not proof.
The problem to which Daniel refers is very old and very difficult (cf. Plato’s Euthyphro Dilemma). Without some final Arbiter of the Good, defining "good" becomes a practical impossibility, as it seems to always defer to some external referent, leading to an infinite regression problem.
However, the regression is stopped if a place can be found where the "buck stops here." Aristotle's Unmoved Mover would be a species of solution to that problem. Of course theists extend that from the realm of pure reason to include divine revelation and such, which is not contrary to reason, but an extrapolation from foundational principles.
Yet Christianity has an accommodation for those who cannot make that leap from reason to revelation. We accept that God has made the universe in such a way that reasonable persons of all theological persuasions, including atheists, can use reason to draw valid conclusions about right moral behavior. Natural law.
So Daniel is simply being consistent with the long stream of Christian thought when he tells you that A) we accept and encourage any logical way of reaching the same conclusion as us on marriage, even when there is no direct reference to God, and B) according to the most rigorous standards of logic, the good arguments you have raised do not resolve the problem of the final Arbiter of the Good. They do not bite through the hard kernel of the problem, but lightly gum around the edges.
And that’s a real problem. If you want society to have moral behavior, people need to genuinely believe in goodness versus badness. Appealing to “survival of the species” is too abstract, and proves nothing. People are practical. If no authentic deity is provided to provide moral accountability, a pseudo-deity will be provided, either in the nature of craven superstition, or by elevating some human elite to play god. Either of these will tend to devolve into totalitarian systems. I believe what distinguishes the conservative from the statist is the intuition (supported by reason) that human freedom depends on avoiding both these errors, relying instead on a higher moral law of divine origin to which we are all accountable. This is the true principle behind the “rule of law,” that no one is exempt from obedience to that universal, uniform standard of right behavior, and no society will get very far toward stability, let alone survival, without it.