Further, I find it incoherent to criticize someone’s superstitions if these are meant to bring some benefits, yet not do so with the optical illusions in Greek temples.
The distinction here pivots on the word “meant”: the optical illusions were indeed meant — consciously designed — to achieve the purpose that they do, whereas religious superstitions have no such clear, designed, single, pro-survival purpose. Attempts to divine one, by cherry-picking a subset that happens to fit and ignoring all those that fall on the other side of the fence, are fallacious. Nor — especially worth noting — do people often subscribe to a religion in order to achieve a survival benefit, whereas art appreciation is entirely voluntary.
Contra-survival religious idiocy is ubiquitous and obvious; e.g., even a cursory glance at US politics will reveal as much more of it as needed to constitute solid evidence. Further afield — Shaker sexual abstinence? Self-flagellation during Ashura? Baby-tossing in India? FGM? — there’s even more. The arguments for “survival of community” are particularly inapplicable to that kind of craziness:
http://www.smithsonianmag.com/smart-news/there-are-only-two-shakers-left-world-180961701/