There is no reason to issue a refund. Even if they hadn’t reviewed you yet, they would still leave you a bad review. Any reasonable guest will be able to tell these guests are NUTS, and the review will soon be off your page.
Do you mean you don’t normally leave reviews?
EDIT: I finished reading the thread and it seems you do not. It is OK to leave a 1-sentence review for an unremarkable guest. Most of my reviews boil down to, “GUEST (party of #) stayed with me for # of nights. They were good communicators, respected house rules, and left the space clean. I would host again.” If they were an adequate guest but we didn’t share a personal connection, what more needs to be said?
Future hosts won’t have this context. Leave the spirituality out of the review.