That's quite a statement.
The inquisition was to stop the advancement of Islam in its tracks. The Muslims went into Constantinople bent on coverting or killing Christians. The Mideast was Christian long before it became Islamic. (Look at your history...)
Stop Islam by killing Jews, Protestants and Cathars. I don't think so. If the Catholic Church could bring back the Inquisition it would. Just like in Iran. Sorry to be so negative, but that is what the history shows us.
The Inquisition was to stop the advancement of "heresies" such as the Cathars and other gnostic sects, along with anyone else whose beliefs ran counter to that of the Church. By today's standards, it's the worst kind of wrong. By the standards then, it still wasn't all that much fun.
My own objection to DVC is that it uses a good ol' conspiracy theory to sneak in a poorly written, poorly executed diatribe on goddess-worship. I was actually amused and fascinated by "Holy Blood, Holy Grail", and would have gone to see a movie that incorporated its elements intact. Brown is pushing some new-age concept of goddess-worship as being the true root of Christianity, and he does it with the vehemence of someone who believes it himself.
Yes, the story is fiction, but the agenda is fact.