Temples to stupidity? Why do you suggest churchgoers are stupid? I've met very few I'd categorise as such. Many are - shock! horror! - highly intelligent, judged by the usual ways we measure such things.
Clearly many churchgoers are intelligent, but many intelligent people do or believe in stupid things. So let's label the belief, not the believer
If someone believes something without evidence, I'd say that's pretty stupid. It might give him great comfort, or cause him to do good things, or even great things that require great intelligence, but that doesn't stop belief without evidence being a stupid act.
It gets even worse when the thing believed in doesn't make sense to the point of paradox. What sort of double-think does a Christian engage in when he believes in an omnipotent, omniscient, omnibenevolent god that allows tens of thousands of innocent people to die in natural disasters?
Are churches temples of stupidity? I'd have to say they are. These are places people to go pray to to change the behaviour of the universe to suit their own individual needs. Catholics go to their church to worship their one god who is three separate entities but still only one single entity, one of which they think they eat the human flesh of. Evangelical Christians go to church to hear how their god created the earth 6000 years ago, and deliberately placed pretend dinosaur fossils in the ground to trick the people he loves. Muslims go to Mosque and hear how their peaceful god wants anyone who stops being a Muslim to be murdered by his followers. Church of England believers go to church and are taught about the bible by women, when the bible says not only that women aren't allowed to teach men, but that they shouldn't even speak in church.
I'll leave 'malign' for another day when teddy bears aren't being named by children...