Like Borat before it, Larry Charles’ Religulous is a semi-documentary that uses its subjects as punchlines in a joke they’re not in on. The difference is that in lieu of the virtuosic Sasha Baron Cohen, we get smarm-meister Bill Maher, whose satirical aim is pretty good as long as he’s shooting fish in a barrel. Maher’s wandering-skeptic act grows thin once it’s apparent that his vanity project doesn’t include any intelligent advocates for organized religion. Instead, we’re cued to giggle at cretinous creationists, snake-oil evangelists and idiotic US senators — easy targets whose variably dangerous irrationality is (one hopes) news to nobody, and whose onscreen humiliation will do little to impress, much less persuade, those viewers who aren’t already onside.