Do you really not understand that you speculating on a theory is much different to show watchers than show watchers speculating amongst themselves?
Let's make a spoiler free example.
Jaime is the one that pushes Bran out of the window at the end of season 1 episode 1. Let's say that his involvement wasn't actually revealed in the episode. But hints are given that Jaime and Cersei were involved (Catelyn finding the golden hair up there etc). Show watchers speculate that it was Jaime that did it. That's fun discussion. A book reader comes in and also agrees that Jaime probably did it. Even if this isn't revealed in the books yet, the show watchers are going to be annoyed. What extra knowledge does the book reader have to say this? Is it actually revealed that Jaime did do it, or are there more hints that strongly indicate it later on? Maybe there's two competing theories amongst the show watchers. Maybe some think Jaime did it and some think Theon did it (for whatever reason). The book reader agreeing that Jaime did it pretty much ruins any anticipation show watchers have towards this mystery.
*a bit of spoilers to extend this*
Jon's parentage is such a mystery. Who is his mother? What would drive Ned Stark, who is such an honourable man, to cheat on his wife and have an illegitimate son with another woman? This is a fun mystery people like to think about. And book readers weighing in on it really take some of it away. You are free to theorize on this with your book knowledge, but do it in another topic designed for book readers in mind.
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The batman villians all seem to be one big joke that batman refuses to laugh at - SantaRPG