I'm shocked, shocked to find that gambling is going on in here!
Data from recent surveys indicate that liberals and people who are not regular churchgoers are more likely to believe the tales proposed in The Da Vinci Code about Jesus having children with Mary Magdalene, said Catholic League president William Donohue.
“There is an inverse correlation between religiosity and belief in the Da Vinci Code's thesis,” explained Donohue in a press release. “The more likely one is to attend church, the less likely he or she is to believe the book's thesis.”
Link.
The reason is obvious, no? Churchgoers just don't want to admit the truth because they have a vested interest in making sure Christ stays divine. It's all very simple.
It's not at all related to the average secularist's sponge brain that sops up anything--water, oil, urine--out of a thirst for some truth, any truth, no matter how absurd.