i dont think the idea of them was ever to become converted by them as soon as they say something (even if that was their intention). the evidence they produce may not always be solid, but the way i see it, the points they raise are really to make me think about the subject, and consider if what seems to be mainstream thought is really the way things are.
admittedly, the fact im a general sceptic, athiest and am generally indifferent to politics probably helped my liking of the show.