. . . So this modern idea that the moviegoing experience is somehow destroyed if you don't go in completely ignorant is bizarre.
While we're at it, the novelization of The Empire Strikes Back came out a month before the movie, and I think David Prowse revealed Darth Vader's identity in an interview a year before the movie came out, and nobody thought it ruined anything. (Although I remember mentioning it loudly to my family on my way out of the theater in 1980 and getting an annoyed look from a passerby going into the theater. . . .)
Back in elementary and high school, my relationship with most of my classmates was always one of mutual contempt (that might very well be why, in my novel and various "Organ Princess" short stories, I've always gone to such great lengths to portray my protagonist as an ordinary girl of the 1970s and 80s, who simply had an extraordinary musical talent [and an IQ to match]). At any rate, though, from first grade to my senior year of high school, I had more friends among the faculty than among my fellow students. And so it should come as no surprise that my pre-calculus classmates gleefully delivered the spoiler about Darth Vader being Luke Skywalker's father, directly to my face, before I'd had a chance to see the damn picture.
I was indeed profoundly annoyed at that. So I can sympathize with your annoyed passerby.
On the other hand, I also remember a sitcom episode in which the "Dad" character, who (for reasons I don't remember) was unable to watch some major sporting event (football, I think) live, and so he recorded it, and went to extraordnary lengths to avoid spoilers. And failed.
I also recall a lecture, and a textbook reading, in (I think) one semester of Short Story Workshop at OCC, that discussed the three ways to build tension. I don't remember what the middle one was, but the cheapest, easiest, lowest-level, and least-satisfying was something like "mystery and surprise," while the most difficult, but most satisfying (and most amenable to re-reads) was something like "tension and anticipation," in which the reader knows damn well how it's going to end, and the fun is how we get there.
(I've written myself a note to look that up this evening. It helps that I can count on one hand the number of college textbooks I've sold back, and have fingers left over.)
Personally, it seems to me that if a story can't tolerate the audience knowing the ending in advance, then it's relying far too much on surprise, and far too little on anticipation. And of course, it also tends to kill the demand for repeat business. Not a big deal for a book, since re-reading is free (and I've lost count of the number of times I've re-read DD's
The Wounded Sky), but definitely a big deal for a movie (I paid to see
Merrily We Roll Along three times in movie houses, then bought the DVD, and all that after I'd already seen three different stage productions, years earlier).