Do directors have an obligation to make totally accurate movies based on real events or do they get a pass for fudging some facts to create a better story?

Remember, about the only thing that Oliver Stone got right in JFK was the date on which Kennedy was killed....

http://www.nytimes.com/2013/02/23/movies/awardsseason/the-history-in-lincoln-argo-and-zero-dark-thirty.html?pagewanted=all&_r=0