From the point of view of any one religion, that code is inherent and therefore "true". In other words not something that is necessary, but simply is. The interpretations of that code and iterations of those interpretations form a spectrum of individual truths, the overlap of which is more or less accepted as the standard.
In the same vein, there are varying forms of atheism (See Re: the weak argument of atheism). Within the varying forms, individuals choose on a issue by issue basis where their particular moral position lies. The variant of atheism I ascribe to, as with any religion, holds those who share that view up to a standard. That including, if one has a worldview that does not contain a supreme being, then one should not hold oneself in higher regard for it.
This speaks to an assumption held by some atheists that absence of consequence makes adherence to a code more noble. Yet, whatever the motivation, compliance to a set of standards imposed from without or within is a difficult challenge. To strive for it is an admirable quality in any human being.
while this holistic position has been attacked as an ascription to nothing, I argue that Derek's posit would lead to similar results. embedded in his argument is the posit that religion is a construct that the world requires to continue running in an organized and civilized manner. In that world religion is a choice.
If religion were to fall out of favor in this world, it would be faced with a spectrum of individual truths, the overlap of which would be more or less accepted as the standard. Invariably those with the most similar codes would group together as groups do with religions, albeit in this argument on a strictly secular basis.
The conclusion being, in that world, Religion would be replaced by new constructs that would serve the similar functions. Again, this argument and conclusion presupposes that religious groups relinquish what is inherently true. whatever that truth may be.