I've been meaning to write a bit on this question, but have been spared some of the time and effort by Greg Wright, who wrote this short but insightful review of TDVC movie when it first came out (oh so many days ago). Wright (who is not a Catholic, btw) observed the following:
Earlier today, MSNBC carried an AP story which reported that Ron Howard's movie "subtly softens" the material of Dan Brown's book. The Associated Press couldn't have it more wrong.
Yes, Tom Hanks' Robert Langdon does find some new dialogue in his mouth courtesy of screenwriter Akiva Goldsman, words that at least play devil's advocate with Ian McKellen's Leigh Teabing. But in the end, the cinematic Langdon becomes much more of a true believer than does his literary counterpart.
Three major innovations introduced by Howard's movie:
First, his film portrays Opus Dei and the "shadow council" of the Vatican as really being in cahoots, really conspiring to kill people in the name of God, really trying to supress intellectual inquiry, really turning its back on truth and righteousness. In short, Ron Howard turns the Catholic Church into a genuine villain. Shameful.
Second, the movie further fabricates ancient history, making the charge that history is unclear whether the Roman Empire or the Christians were the first agressors. Please!
Third, and most importantly, the film invests significant energy in validating the Magdalene myth. While in Brown's book Marie Chauvel basically leaves the existence of the Sangreal documents and Magdalene's bones to the world's imagination, Howard has Langdon and Neveu discover plenty of material evidence to back up the claim.
Where's the mystery that feeds the soul? Where's the adventure? You'll have to find it in the book, I'm afraid. There's no codebreaking here, just polemic.
These are excellent points — but they were missed (or ignored) by most other reviewers of the movie. For many reviewers, the unforgiveable sin of Howard's flick is that it is ponderous, boring, silly. But Wright is absolutely correct that movie, just like the novel, is much more about polemics than storytelling. Which is one reason the storytelling is so ponderous, boring, silly. Which, happily, blunts some of the polemics, but hardly exonerates the filmmakers from going to such lengths to disdainfully (or is it "dis-Dan-fully"?) attack the Catholicism, historical fact, and commonsense.