Good essay. I have often thought that the very institutions of belief
I despise in most contexts may serve important social goals that it
would be dangerous not to replace; thus I have suggested creating new
mythologies, holidays, gathering functions, etc. Perhaps even the
irrational beliefs themselves serve some of those functions. I would
not hesitate to create church-like or state-like social systems by
voluntary association to fill some of those roles.
Although I think you ignore what to me seems like an equally likely--
and more cynical--posibility: that people associtate with belief-
based social groups specifically to /hide/ their true beliefs. That
people may be active Democrats, for example, to make people think they
care about the less fortunate without having to actually do any of the
hard work of genuinely caring.