Some ideas matter, most are cast aside or ignored entirely. I’m not sure movies are a contributor to societal beliefs in the way books were and still are.
Movies reflect the belief of those who produce them. I have yet to see a movie that could alter my beliefs.
This argumant comes up often when people are discussing the effect of TV, you know, the medium that doesn't effect anyone's behavior but is funded by 30 second long film shorts designed to successfully effect behavior.
Seriously, if you think the visual media haven't been as influential as books, consider where sexual mores have gone in the past generation or two.
I have yet to see a movie that could alter my beliefs.
How do you know?