Why does the age of the movie have any bearing on this? We aren't born with all knowledge of previous movies. There will only be more and more of them released as the years go on. For most of us it isn't possible to watch and know all of them. I don't think it's too much to ask for a heads up when a spoiler is coming.

If this was a community based on the movie I'd say all is fair, but since it isn't I don't think it is fair to dismiss the concern just because the movie is old.