With all due respect.
I'm a Catholic. I "converted" 6 years ago. I listened to The Da Vinci Code on CD and loved it. Historical fiction is great. Was it Anti-Catholic? Maybe. Was I offended? No. Did I feel the urge to leave the Church? No. Did I do some research into the organization the book talks about? Sure.
What's the harm?
The Cardinal asks what would happen if someone wrote a novel that was Anti-Islam. Ask Salman Rushdie how that has worked out for him.
What a great opportunity for Catholics (and/or others) to inquire about their faith. Read the book, and then ask your priest about it. Have your priest read it, and then ask him lead some discussion groups about the genesis of these ideas, and explore where they came from and where they deviate from doctrine.
This isn't heresy; this isn't blaspheme.
The Avatar Meher Baba once stated that it is important to question your faith. If you truly believe, the questioning will only make it stronger.