I don't feel like that at all. I would feel it a personal victory if I was able to guess the ending of a movie (by AC you mean Advent Children?). You can't ask people NOT to make up theories, because they have all rights to do so. If you don't like that, then maybe the forum life isn't for you.
Personally, I like to keep with the facts. But to use those facts to make a theory to explain something, like a plothole, is fun and interesting to do, as you recognize it as a theory and a theory only. Looking at Arbiter's smoke aura and making a theory of a demon soul being caught in that weapon is just a theory until a fact has either proved or disproven said theory. Theories aren't spoilers and you cannot stop people from making them.
