Isn't it paradoxical to speak of the modern zeitgeist as "skeptical naturalism," and to call that outlook an "unquestioned cultural assumption"? The outlook is precisely that everything should be questioned. It's skepticism that turns into cynical "postmodern" distrust of all authorities and metanarratives.

Atheists and secular humanists are in line with that zeitgeist, in that they're much humbler than religious dogmatists. It might seem, on the contrary, that secular humanists are hubristic for believing that we can solve all our problems, but there's a difference between trying to do so and knowing for certain we'll succeed. Only the latter might require something like religious faith.

It's quite possible for a secularist to think that our godless civilizations are doomed to fail, but that we have no other option except to try because the gods are obviously dead--as in they're no longer live options for motivating the social enterprise, regardless of what the hypocritical masses might say with their superficial religious faith.

I agree that when we dismiss something as preposterous, we do so ultimately based on a lot of evidence. But the gathering of that evidence can be deferred. It's modernity as a whole, including the last several centuries of science, philosophy, technology, capitalism, and democracy that supply that evidence in the case of the atheist's dismissal of theism. So the atheist needn't personally look at all the evidence to back up the rejection, since that would be like reinventing the wheel.

My next article won't be the one that replies to yours since I have a backlog of articles. But they're almost all on point as clarifications of the nature of atheism.