Rejection of All that is Holy

[Neo-Scholastic]

…you're still trying to categorize atheism as a rejection of a proposition (it isn't) that necessarily entails an additional rejection of supernatural beliefs (it doesn't.)

I made a special effort to avoid that entailment by always including the term divine. You don’t have to be a theist to believe in ghosts or magic.

But that said, I do say it, atheism, is the rejection of a proposition, because the proposition is already embedded in Western culture in subtle and pervasive ways. For example, in the natural sciences, people talk about various laws, like the laws of physics. This use of the term ‘laws’ is based on a thoroughly Christian concept, i.e. that the regularities observed in nature, i.e. ‘laws’ are the result of a divine lawgiver.

… I doubt you'd find an atheist here who, when presented with a clear, unambiguous divinely inspired spiritual experience, for which no more likely explanation can be found, would actually reject it.

We are both trading in speculation here. I suspect that self-identifying oneself as an atheist affects how one judges what is or is not a genuinely mystical experience. Consider how easily many posters will say that mystical experiences are delusionaa

…Disagreement is not rejection…atheism simply disagrees with the claim that currently observed spiritual experiences are divine, mostly owing to their vague and subjective nature.

Within the context of this discussion you are making a distinction without a difference. If someone disagrees with an opinion, even if their reason is that the statement is too subjective, that means that they do not receive it. Instead he or she turns it away, i.e. rejects it.
Secondly you call spiritual experiences ‘vague’. By doing so aren’t you making a value judgment from within an atheistic framework. I doubt very much that GodsChild or Drich would call the reply to A/S/K vague. I am not asking to accept that their experiences are actually divine. I ask you to recognize that you are taking a stance that is opposed to accepting them as divine.

… Can it really be called a rejection at all, if the threshold for acceptance is "must be really divine"?

The threshold is the problem that concerns me. To set a threshold, culturally and personally, is an act of establishing the boundaries of what is acceptable to think and how one must think about something. For example, the position that requires ruling out all natural causes before allowing for divine causes reflects a bias toward scientific modes of validation that are currently valued in Western societies. I suspect the same is true of the words ‘atheist’ and ‘atheism’, the terms set up conceptual boundaries within a larger cultural context.