No, the reason religion is excluded is because delusions aren’t supposed to reflect cultural conditioning. Delusions are, by their very definition, an abnormal brain process. Cultural beliefs are not abnormal brain processes, no matter how irrational they are.

That's what i'm saying, the reason that cultural beliefs aren't allowed to be delusions is simply because they don't want to make religion a delusion. It's common, so, it's not a delusion. That's the end of the reasoning. Should we really say that anything that's commonly believed isn't a delusion? I think that's an exception made for a logical reason, it defends the field of psychology from culture, but cultures can share delusions.

Please understand that this exception is accepted by the entire field of psychology. If you disagree with it, you have 200 years of psychological debate and study to contend with. Don’t pretend you’ve read enough to claim you have grounds to disagree with something the entire field of psychology considers a settled issue. No matter how much you wish religion is a mental illness, it’s not. Sadly, the irrationality of religion is fully explainable within the bounds of normal human psychology.

The reason this exception exists is precisely as i've said, they've special cased it because they don't want to define religion/cultural beliefs as mental illnesses. The very reason for this exception is because they don't want it to count, not because it doesn't meet every single other (much more important might I add) criteria.

they're essentially going "yeah, these are delusions, but uh, enough people believe them and we don't want to piss them off so here's an exception"

I personally don't think that's valid at all, but I can see why they'd do it.

Just because a delusion is normal to have, doesn't mean it shouldn't be a delusion.