Actually, I think changing a whole story itself should be a crime. Really. Because there's no need for that. If movie makers don't like the original story, then what's the point of adapting it in the first place. None.
Any inaccuracies bother me. However big or small, and it does tend to ruin the film for me. I think accuracy in movies, and books, is really important. Maybe teeny tiny things that pertain to the desired outcome can be changed around (though it would still bother me), but historical events and what we might know about the character of a person should NOT be changed at all! If either of these things "need" to be changed, then don't make the movie -- because they should not have to be changed. Also, it's kind of insulting that these movie makers seem to think that, what, maybe we won't notice? Always nice to know what they think about our intelligence.