The Trolley Problem and similar probes into morality have shown that all viable cultures are in agreement about what actions are moral (sorry quote keys do not work). They even extrapolated their questions to primates and found the same responses.
http://www.joshua-greene.net/
Once religion gives up the mantle of moral leadership, what is left that we should support. At a dinner party this last week I brought up your arguments and the best response I got was that religion might act as a cohesive factor to promote a sense of community. If this cohesiveness is at the expense of cooperation with others then it is worth very little.
It's the capacity of religion to give people a cohesive foundation upon which to operate that doesn't depend on rational understanding that seems on point to me. With respect to cooperating with others - well, to me that depends what those others are doing. I foresee post collapse that a significant number of fragmented groups will remain. Some will merge, some will fade out, and some will continue to compete - history repeating itself.
Many will adopt non sustainable approaches, which seems to be normal for most human societies across history. I see no case for cooperation with those, as that thinking is indirectly a sort of warfare in its own right - the appropriation of resources today from those who could use them later (and this including
renewable resources such as fish stocks, which can be converted to non renewables for short term advantage).
So how can one ensure a sustainable ideology comes to dominate and outcompete all those groups unlikely to be operating that way? I don't see how cooperation is viable, and short term unsustainable behaviour grants a competitive advantage (hence it's so popular and widespread), making it a priority to eliminate that thinking early and aggressively.
The only idea I have so far is that the sustainable ideology must eliminate non sustainable ideologies - through warfare if necessary. I realise that's a rather ugly idea, but how better can we safeguard the future?
The argued value of religion here is the ability to create dogma and fanaticism - morally ugly, but a practical candidate solution to a rather intractable problem.
Even today, with all our education, science, and knowledge - we operate unsustainably - in fact - we leverage the former to do so more effectively. Rational thinking doesn't therefore seem effective at getting us to a sustainable paradigm - leaving what?
Arguably, this isn't an end goal - merely a way to buy enough time to usher in rational thinking that is sustainable. For example, would we have rushed to adopt combustion technologies using fossil resources had we generally realised from the outset what the consequences would be? One would hope not - although... one has little faith in people.
I probably erred with my emphasis on slavery. I had merely attempted to use it as an example of things that we now consider reprehensible that were defended and institutionalized in certain religions. Child marriage, stonings, the Children's Crusades, and others would have done as well.
Morality is a tricky area though? It's interesting if the trolley solutions are universal as part of human nature - but it seems to me a lot of things vary greatly within societies. I have done my fair share of things that some might say were immoral, because even though I haven't sought to cause harm to another in any clear fashion, I might not have always obeyed "the rules" as mandated in various jurisdictions, and some call that immoral. I call it practical, because too often in life there are no nice choices available (and besides, what value do "the rules" of modern society really have, when it's doing what it is?).
I will do my best to pass on what science and engineering books I possess, and will have no qualms about tossing any religious texts to make room for a few old issues of Mechanics Today. The dark ages saw the rise of totalitarian theology & it took hundreds of years before the age of reason dared raise its head. Adding another layer of superstition is not (I hope) the way forward.
I wouldn't hesitate to toss (and indeed would proactively discard) any existing religious texts. They are competing unhelpful ideologies, and not sustainably founded (look at the propensity for religions to promote population growth for instance). I'd be tempted to tear out pages on combustion technologies from the more rational texts too - though I'm not sure if that's necessarily a good idea or not.