>>> It was fiction. So there was no claim of truth. <<<
I haven’t seen the movie. I’ve got the book.
In the book, there may be no explicit claim of “truth.” There is a significant and clearly-made claim of “fact.” For most readers, that’s a difference that makes no difference.
The FIRST WORD of the FIRST PAGE of the book is (in big, bold-faced type) FACT.
What comes after that word is what Dan Brown wants us to take as FACT: his version of the Priory of Sion, his version of Opus Dei, and that “All descriptions of artwork, architecture, documents, and secret rituals in this novel accurate.”
Given that the movie was so closely tied-in with the book, your claim that “there was no claim of truth” is preposterous.
To imply that makers of movies and writers of novels — especially polemical or propaganda novels — haven’t changed a lot of minds (and made a lot of money) eliding the difference between FACT and FICTION over the years is just plain goofy.
If they have changed minds it’s weak minds. No work of fiction no matter great (or in this case probably really bad) should be taken as a history lesson.