I tend to think that when indulging in conspiracy stories, even if known to be false, one must actually believe a little of it. Otherwise, there would be no compulsion to continue with it. You write about what you are interested in.
I think Brown is most interested in symbols and codes and so on. That is the part of it that does it for him more than the rest of the story.
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.