Finally coming to the question, is the aversion a matter of wanting to avoid a confusion of terminology (belief with faith)
This is usually the biggest reason for the aversion I've personally noticed. Atheism/agnosticism/etc. may be a belief, but it's not a belief in the same way a religion is, and most of the people that call atheism a belief seem to be the sorts that are trying to say it's explicitly the same as a religion, complete with tenants and rituals and all that rigmarole. And it's not. There's not even a secret handshake or somethin'. It's not a belief in the religious sense, it's a belief in the epistemological sense.
Atheism isn't even a loose confederation, really. There
are some atheist groups of thought that do collaborate to degrees (this is why you do at times have atheists acknowledging each other as the same sort of critter in public), but that has little to do with the general belief itself. Calling atheism a confederation is about the same as calling people who like milk a confederation, y'know?
or is it a means of differentiating between spiritually and materialistically (I don't mean here the negative connotations, merely the relation to matter and natural laws) founded beliefs
Metaphysical and non-metaphysical would probably be better terms to use, heh. That's part of it, but as usual not the whole.
Secondly, Atheists and Agnostics, have you studied theologies and the philosophies that go with them? Were you educated by its proponents-- not its opponents-- in them? What about other atheists and agnostics you know? As regards my own faith, who and/or what did you learn about Christianity from, if you have studied it?
Irreligious apatheist here, which is more or less a specific sort of agnostic. I've actually sunk a few years into theology, via philosophy education (I've said it before, I think, but I find theology to be very pretty.). Medieval christianity, general philosophy of religion, bit on eastern religions... most of it taught by a couple of christian priests, though I've since forgotten their denominations (and it wouldn't really matter for one of them, because that one was
significantly radical). Beyond that, I grew up in an almost blanket christian area, and did go to church/sunday school for the earlier years of my life, though my parent was never particularly religious and regular churchgoing stopped probably around 5 or 6. I've never really been explicitly educated by opponents to any faith, much less christianity -- even the folks that weren't religious or some variant of theist were pretty okay with faith or religion as a general thing.
Unfortunately, beyond never experiencing the precise sorts of hallucinations that convince people their belief in a particular religion is true (I had
different "religious experiences" that were unfortunately entirely too identifiable as hallucinations to convince myself otherwise), I, as mentioned, grew up in an area that is pretty much blanket christian and very, very vocal about it. Three churches in a two caution light town, that sort of thing. I've pretty much never actually, in person, seen the church or the faith produce something that wasn't toxic to some degree. I've met wonderful people whose love and light turned their faith into something that was positive -- some of the best folks I've ever met were religious of some sort -- but generally religion just seems to produce nastiness after nastiness. Comfort for the folks that are immediately involved (which, to be fair, is a certain sort of virtue), but gods help you if you're not.
That's where the irreligious comes from -- I've reached the point I'm fairly convinced that organized religion is a net negative. Individual faith of whatever sort I'm pretty okay with, but the organized sort just seems to consistently cause problems. Worst bit to me is that some of the worst problems always seem to be regarding following the religion itself -- few things seem as capable of leading a person to violate the tenants of their religion as a priest and congregation. For living in an area that preaches love as one of the highest tenants of their belief, I have seen a
lot of hate in my lifetime
Combined with the lack of any explicitly identifiable effect on the world, I got turned off pretty hard, and it eventually reached the point where consideration of the question of divinity has pretty much no meaning to me beyond idle amusement (which isn't necessarily a bad thing,
per se. Idle amusement is good.). That's the apatheism -- I don't think the question of whether there's a god or not actually matters. The answer is irrelevant; the world changes naught one bit whether there is or isn't one, insofar as I've been able to tell. If you want to get me to care enough to really fall into a theist/atheist camp, you'd have to convince me it
matters, that the existence or non-existence of a god actually has an effect on the world I observe. As it is, it's fun to talk about, but that's about it.
Doesn't help that the natures ascribed to the divine are generally pretty nasty themselves. I'm arguably happier with it not mattering than I would be if it did, heh.