"My grandfather smoked and drank until he died at 86. That is NOT evidence that smoking and drinking are healthy. The other factors that allowed him to live that long could be viewed as coincidence."

You don't appear to know what "coincidence" means.

"Well I think the question is 'If it works, if it requires faith, if it is a benefit that people have enjoyed for thousands of year, if it is a net mental health benefit, how can it be a delusion?'"

Simple. If it's wrong, factually incorrect, utterly misleading, false, a downright lie, it's a delusion. The benefits you claim for religious belief are available without that belief. No faith required. Lots of us have tried it and it works. Rudders, not crutches. Religious belief often comes with an awful lot of strings, some of which are used very effectively (and deliberately) to strangle the intellect. As this thread shows in abundance.