I have a friend who's little sister has made a career out of spoiling movies. I wish, I were exaggerating, but every conversation about a new movies literally goes like this:
Her: Hey, have you seen [movie] yet?
Me: Not yet, but I really want to see it this weekend.
Her: Oh, it's really good! There's this part at the end where they find out that Soylent Green is people!
Me: What the fuck?!
Hell, she's even spoiled movies as I'm watching them! "Oh, is that Gladiator? It's sad when he dies at the end." (I'm trying to pick movies here that I'm sure either everyone has seen or doesn't care about, but you get the idea)
I guess my point here is that it's perfectly reasonable and not juvenile to get severely pissed off when someone spoils a movie or game for you, especially if you're looking forward to it.
If I were to find two unlikely people who have never seen Saw or The Sixth Sense, make them watch the movies, but tell one of them all the twist endings, who would appreciate the story more? Having the end spoiled just ruins the experience.
Apologies to anyone who, for whatever reason, never saw Soylent Green or Gladiator.