Also, aren't visions of the future explicitly unreliable because it's always in motion? Why is this one, which is apparently unique in the universe, absolute and concrete while all others are only possibilities that may not come to pass?
Given what the Jedi know, its certainly reasonable for them to not give full faith and credit to the prophecy, and even if it wasn't, it's not as if Anakin had a tattoo saying "totally the chosen one" or anything.
It's hard to deal with because the entire concept was just horrible writing.