Clearly anyone who thinks this book is about unraveling and Ancient Conspiracy, is offensive to Christians, or finding the Holy Grail has not read the ending. The Conspiracy Theorist who presents the entire background of the quest turns out to be the villain behind the whole plot, the conservative Bishop ends up just being out to save his Church because his followers have a bad reputation thanks to the media, Silas was far removed from the norm of Opus Dei, but even he is wracked with guilt and regret, and the Priory is Sion is shown to be all but purely symbolic. They never even intended to "reveal the secrets" to the world because that is not the purpose of the secrets. Langdon ends up following the final clue back to where the story began, but instead of trying to uncover the bones of Mary Magdalene and show the truth to the world (which isn't even confirmed to be true), he kneels before the symbol of the sacred feminine and pays his respects to what it represents. The purpose of the quest was always to find the truth, but in a spiritual or metaphysical sense. The ultimate purpose of this novel is not be be correct (the author is the former trope namer for Falsely Advertised Accuracy after all), but to encourage the reader to think and open their mind to new possibilities without outright rejecting the old ones. It is an Author Tract on spirituality masquerading as a conspiracy thriller.
If the Holy Chalice (aka the Holy Grail) is an allegory for Mary Magdalene, and the Gospels of Matthew, Mark and Luke describe him passing the Holy Chalice around during the last supper, that means he was actually passing his wife around to his apostles. So basically, The Da Vinci Code tells the story of how Jesus was a swinger.
