The five words that are most poisonous to cinema are not “would you like some popcorn?”, though that itself is irritating beyond belief. Rather, it is “based on a true story”, that irksome phrase which strives to give legitimacy to even the most fictionalised account.
The problem is not so much the idea of films about actual events. Rather, it is the claim that they are “based” on a true story or “inspired by real events”. This means “we’ve taken a story, changed it to make it more interesting and we’re still going to sell it as fact”. The end result is that you’ve got a story you can’t really get into because you spend half the time which bits they made up.
Now, this is not to say that I am against historical fiction. I am not. Historical fiction can be an interesting and enjoyable experience, but it is best when it makes no claims to authenticity. For all its flaws, Titanic worked because it wasn’t bogged down trying to tell the true story of some people on the actual ship.
What I am against is the use of the claim as a selling tool. It mixes truth with fiction so that the best scenario is that people are entertained by equally as ignorant of the original event as before the movie. The worst case is that they hate the movie and come away thinking they’ve learnt something when in fact they haven’t.
The one exception to this rule is the horror genre, though only when it involves supernatural activity. The reason it has no negative effects here (though no positive effects, for the most part) is that that is all made up anyway. If you believe in ghosts, it doesn’t matter what a movie teaches you about them. If you don’t believe in ghosts then it can work on the level of pure entertainment.
However, when you put it in something like The Impossible, it’s hard to let yourself be absorbed into the action. If it had not been supposedly based on a true story then I would have enjoyed it a lot more because I like my facts to be factual and my fiction to be fictional.
In future, to avoid any such confusion, all made up scenes in “based on a true story” films should contain bright red flashing subtitles informing viewers that “we made this bit up”. Sure, it might be distracting, but surely no more than the uncertainty of historical inaccuracy.