In a way, Roman Catholics reading The Da Vinci Code should be flattered. After all, according to Dan Brown's vision of past and present, the only embodiment of Christianity the world has seen is the Roman Catholic Church.
This is, of course, not quite the case. For example, much of the theological action in question--the formation of the Canon, the discussions of Jesus' human and divine nature--was centered not in the West, but in the East, and involved mostly Eastern bishops. Eastern Catholic and Eastern Orthodox Churches embody that ancient tradition just as deeply as the Roman Catholic Church does.
And then, of course, there are the Christian churches that emerged in the wake of the Reformation, which despite deep differences with Catholicism and Orthodoxy on issues ranging from justification and salvation to sacraments, still continued to affirm the traditional doctrinal understanding of Jesus' human and divine nature as found in those early creeds. Those understandings are what Brown's scholar-character Leigh Teabing asserts violate the "original history" of Jesus. Some also engaged in just as much heretic and witch-hammering as the Roman Catholic Church (Catholic bishops, for example, weren't in charge in 17th century Salem, Massachusetts).
But for some odd reason, it is not "Christianity" that Brown identifies as the culprit, the enemy of the true intentions of Jesus, but only the Catholic Church--consistently, and without exception. Orthodox and Protestant churches all affirm the divinity of Christ as defined by Nicaea and other early church councils, all accept nearly the same canon of Scripture, and, in the case of Protestant churches that have diminished the role of Mary in their theology and practice, might merit more criticism for banishing the "sacred feminine" from spirituality far more than Catholicism does.
So for this reason, there might be a case for characterizing The Da Vinci Code as anti-Catholic. It's not just that Brown makes assertions about Catholicism that are not true, but that he also chooses to make the Roman Catholic Church guilty of crimes--misrepresenting Jesus, repressing the "sacred feminine," and rejecting the true leadership role of Mary Magdalene - that, if you're going to follow his logic, for which all Christianity should be judged guilty.
Why did he do this? I suppose because it's simpler, that's why. That's the most charitable guess. It makes for easier writing and easier reading. Not more truthful writing, mind you, or writing that's more faithful to the complexities of real life and real history. For that would be a bit more difficult to do than pulling out stock villains in flowing robes, funny hats toting suitcases full of money.
So according to The Da Vinci Code, Catholics are the only Christians?
Well, maybe, as I said, Catholics should be flattered. We can probably understand if they're not.