Again, my point is not "my opinion can never be wrong" it's "opinions about art can't really ever be wrong."
There's more interesting ways to discuss films than trying to convince the other person that you have better tastes than they do or that your opinions are more correct.
That's correct, but opinions about art can be superficial or poorly founded. If someone came up to me and said "I liked Ghostbusters 2016 because I find Chris Hemsworth attractive," they're absolutely within their right to do so, but there isn't a whole lot of room for me to discuss the film beyond Chris Hemsworth's attractiveness if they aren't interested in considering all the other factors at play.
I've had my mind changed about films, games, and shows plenty of times because of different opinions that had compelling arguments behind them. I used to defend Metroid: Other M because it "gave Samus a character," until I discussed the issue with someone and realized that she already had a character that was in fact being contradicted. The phrase "I didn't think of it that way" is, for me, one of the most powerful tools for intellectual development. I think the subjective nature of art (i.e. there is no one "correct" answer to the question of whether or not a film is good or bad) is what makes discussions of quality so great, because it means everyone's argument is forced to stand against each other and everyone gets a good mental workout considering new perspectives.