From the very beginning, the movies have found it easy to alter what may have actually happened in the world.
Around the turn of the 20th century, supposed documentary footage of the Boer War in South Africa was filmed in New Jersey. Ever since, films are either "based on actual events," or "inspired by actual events" — claims that typically indicate that what's coming is fiction. The cinema is voracious. It gobbles up books and spits them out unrecognizable, and does the same with what we might call reality.
In many cases it doesn't matter.
I doubt that Charles II of England would recognize his own life in Forever Amber or The Exile, but those 1947 portraits of the late 17th century king have no effect on the world's basic knowledge of him. They're melodramas embedded in minor situations. Historical films like All the President's Men and Malcolm X create personal dimensions for their stories for dramatic reasons, but fundamentally they leave the historical record intact. In macro terms, the man Malcolm X is portrayed as a powerful figure in the Civil Rights Movement who was assassinated at a public meeting, and who did it is still unclear. Washington Post reporters Woodward and Bernstein broke and followed the Watergate story and the downfall of Richard Nixon. The movie's inventions about what was said in private or at editorial meetings or with Deep Throat in the parking garage are outside the public record. History rarely has access to pillow talks.
The very idea of accuracy is unruly. Joe Nocera of The New York Times went on a rant about the inaccuracies of Steve Jobs. The things that bothered him most were not questions of the public record of Jobs's life. Nocera was objecting to things about the character and personality of Steve Jobs that he said the movie either got wrong or overlooked. He was annoyed that the film showed Jobs as cynical rather than visionary. Even the most respected historians have to interpret events or historical figures, and if someone disagrees that doesn't invalidate the interpretation, it just means there are other possible interpretations. It's when substantive and known events get changed that you can talk about misrepresentation.
For instance, Trumbo makes actor Edward G. Robinson into a bad guy, and indicates that Robinson's testimony helped put Dalton Trumbo in prison. It didn't. Robinson's testimony to the House Committee on Un-American Activities was indeed slimy, self-serving and damaging to others, but Trumbo was already in prison when Robinson testified. The movie accuses Robinson of something he didn't do. The movie Selma misrepresented the known actions of President Lyndon Johnson.
Filmmakers like to dismiss the idea that they have a responsibility to be accurate about people and events in real life. "It's just a movie," they typically argue. Aaron Sorkin, who wrote both Steve Jobs and The Social Network, asked (in New York Magazine) "what's the big deal about accuracy purely for accuracy's sake?" Well, accuracy is not frivolous, but like most things, there's a continuum, and some accuracies matter more than others.
The Big Short has two historical threads going. One has to do with the economy and financial instruments like credit default swaps, and it's important to get right just what they are. The other is about non-public thoughts and conversations of the characters. Motives, for instance, can never really be known, so to speculate – to imagine – is part of what movies have to do.
Movies matter. They have real effect on what millions of people know or think they know about the world.
The very influence of the movies brings to filmmakers the responsibility not to lie. They can invent; they can interpret, but if they change what we know to be true, they cause harm. In the post-modern world, truth is often treated as a matter of opinion. An editor at NPR once said to me that "opinions are cheap; he needed trustworthy reporting."
Literal truth is not at odds with art.