Has it not always been entwined with religion, though?
IMO it's compromising something that shouldn't be compromised. It reminds me of when my jw parent calls gay partners "friends" or "roommates". She cannot bear to speak aloud what it really is, because it's distasteful to her.
It should be socially acceptable to claim to be an atheist without tempering it with religion-based words. It should not be distasteful. That would be the mark of a reasonable society.
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Edit: I have changed my view on this over the years after thinking a great deal about it. @ first I defined myself that way, but I quickly learned this was offensive to many atheists. My immediate reaction was that is silly, but I came to understand and agree.
It is not possible to be "spiritual" without a religious framework. Belief in the supernatural is religious.
Here is an article on it.
Respectfully, ~me