I've read some reviewers complain that Maher "made to look foolish" the faithful he interviewed. Maher simply asked them questions and reported their foolish answers. Religious nuts, apparently, don't like mirrors.
Another religious apologist asked, "Was Maher afraid he might muddy his clownish jape if he actually brought into the mix a learned theologian." Actually, that tactic has been tried (The God Who Wasn't There and The Lost Gospel of Judas) and religious nuts liked it even less. "Learned theologians" tend to be as agnostic as they become historians or scientists. The more you know about the history of, for instance, Christianity, the more you doubt. Obviously, Maher consulted with many learned theologians, because his timeline of Christianity was accurate and his knowledge of the history of the Bible and the things actually in the Bible exceeded that of the Christians he interviewed. In fact, most of the professed "Christians" know less about their religion than the average uninterested agnostic.