Well, either he deliberately intended to foment bigotry, or he's an ignorant bigot who can't help himself. I'd say probably a mixture of the two.
His treatment of the Catholic Church is despicable.
Much of the discussion was about the Jesus/Magdalene marriage angle. Several said "I don't have a problem with the idea of Jesus being married. If he came to earth to live a normal life, whut's wrong with that?" Even the host made reference to Jesus coming to earth "to set an example for us by living a normal life". None of them seemed to consider that (according to orthadox Christian thought) Jesus was God Incarnate, who came to earth to be the substitutionary sacrifice for the sins of His people. Therefore, He was not termpted to "get some" as a human might be.
I did not hear any discussions of some of Brown's other claims (such as the particularly ludicrous one that no one worshipped Jesus as divine until the time of Constantine), but one caller made reference to "a bunch of Bishops deciding whut oughta be in the Bible, and gittin' rid of whut they didn't like, etc"
It's clear to me that with so many so-called Christians stating that the book "deepened their faith" the real problem is not Dan Brown and his book. The real problem is that many Christians are unfamiliar with even the most elementary Christian doctrines, and will fall for any screwy idea that comes down the pike. Those so-called Christians were lost before Dan Brown put pen to paper because they didn't believe in anything to begin with.
It seems reasonable to me that he holds some degree of anti-Catholic bigotry. He either believes there is some truth in it or he wants there to be.