Ugg, what a mess.
To start with, I’d wager that opinions offered via the SDMB have very little in common with how one would approach strangers or friends in meatspace. We’re an anonymous message board, after all, so we’re hardly indicative of how many people would behave with their coworkers, family, etc…
Now, as for most of the rest of the bickering, there is really only one solid issue: epistemology.
A non-belief in an unproven claim will always be superior to believing that claim. People rationally reject ideas of the Tooth Fairy once they pass a certain age but Yahwey, Allah, God, Zeus, what have you… sticks around much longer. Though there are certainly psychological reasons why that might be but I won’t touch on them here. And while I’d never tell anybody that they don’t have the right to believe as they will, I would argue the issues of epistemology, especially if it’s on the Dope.
Now, many of the quotes that the OP cited are absolutely true, and some are hyperbole. Would many adults accept a religion if they were raised to be materialists and rationalists? How could they choose? All religions make unprovable, untestable, unrefutable claims. Why would someone raised on empiricism and reason believe that Jesus was more than flesh and blood any more than believe that Mohamed was the last prophet of God? Would they believe that Odin the Allfather spent three days dead on a tree in order to learn the Secret of the Runes? As has already been stated, to most theists the religions of the past are simply quaint superstitions and myths. Most non-theists (or atheists if you’d prefer) simply extend that philosophy to whatever sacred cow the theist is protecting.
And it always tickles me when the the absurd “a-theism is the same as theism” meme is trotted out, yet again. Whee. Not believing that there’s a Unicorn in my closet is not the same, epistemologicaly, as believing that there’s a Unicorn in my closet. A burden of proof exists, and though we can ignore it, that doesn’t make it go away. Just as some have said that we don’t know all there is to know about the “supernatural”, I’d counter that we have no reason to even believe that there is anything which is super-natural.
That’s like saying “Well, you’re so certain that there’s not a Unicorn in your closet, but that’s arrogant since you don’t know everything about the Marshmallowverse. What, the Marshmallowverse? That’s the secret world just outside of ours which sets all the rules here.”
Yes, whether or not there’s anything ‘outside’ of Universe is definitely untestable and unknowable, but it’s also just semantic noise. One can be just as confortable in saying “There is no God” as “There are no pixies who sprinkle pixy dust to give us good vibes.” Because, after all, there is no good reason to accept God while rejecting the good-vibe pixies. So while there may be a God or Gods, it’s pretty much on the same level as the possiblity of fairies and elves.
So I suppose in summation I’d say: If you don’t want to have your beliefs challenged in meatspace, don’t talk religion with your friends. If you don’t want to have your beliefs challenged on the SDMB, don’t post or read here.