Well, not necessarily because it's true. There's a lot for the Catholic church to be mad at without it being true.
When I read the book, when I was maybe 5/6ths through I was thinking HOW did he get away with this? Then he did an about-face at the end on some of the issues I was marvelling at -- the corrupt pope turns out not to be corrupt, whatever. (Cop out.)
I read this book for my book club, and the previous book was "Skipping Christmas" by John Grisham. Somehow, the discussion of that book led to the history of Christmas. I made some offhand comment about the Pagan origins, and the Christians in the club were horrified. HORRIFIED. No no it all started with Christ yadda yadda.
Then the next meeting was "DaVinci Code", and I was like "this is what I was talking about!!!" I brought a couple of textbooks. :-) But a lot of these people really had no idea of any of this.
I was raised agnostic and have long had an interest in religion as a sort of a folkway, have studied it (minored in mythology), my perspective for a long time was that Christianity marketed itself to various pagans and such by letting them keep their festivals, for example, just with a new sheen of "Christian meaning".
Also know that the bible has been translated and retranslated and retranslated and like the classic game of telephone, a lot of the original meaning is skewed. There was something about, when you go back to the original text, it being clear that one (pope? prophet? someone you wouldn't expect, I can look this up) was female.
But these ideas were new to a lot of people in my book group, and they were exposed to the ideas by "The DaVinci Code." A lot of them were seriously questioning their faith based on it. This was all a bit incomprehensible to me, but I know it is happening.
So without the whole Jesus-had-kids thing being true, there are fundamental assumptions in the book that are true and that freak out the church, sure.
Quote:"There's a great anti-Catholic prejudice," Bertone said. "I ask myself if a similar book was written, full of lies about Buddha, Mohammed, or, even, for example, if a novel came out which manipulated all the history of the Holocaust or of the Shoah, what would have happened?"
If it was about Mohammed, it'd earn the author a death sentence. (Salman Rushdie...)