Something I posted yesterday (I think) over on the "What's Wrong With 'Folk Music'" thread is relevant to this discussion. I quote my very own self:
"I'm utterly baffled at the "but things didn't really happen that way back then" objections to the "O Brother" film. We're talking about the Coen brothers here. They gleefully make knowing, deliberate changes to history and reality in this film, such as having Pappy O'Daniel be governor of Mississippi rather than Texas, having Baby Face Nelson still be alive at the time the movie's set, having Klansmen do a Busby Berkley at a cross-burning, or having a dammed reservoir flood suddenly. They "based" the movie on the Oddyssey the same way "Fargo" was "based on a true story": not at all. They openly admit to never having read the Oddyssey (I think they're lying: they grew up in St. Louis Park, where the schools are quite good).
"I mean, come on. These are the guys who made "Bood Simple," "Barton Fink," "Raising Arizona," "The Hudsucker Proxy," and "The Big Lebowski." Anyone who expects reality from a Coen brothers film just ain't been payin' attention, and is missing the point. They're storytellers, not historians."
Okay, end quote. To bring it back around to the current discussion, it makes about as much sense to subject "O Brother" (or really any Coen film) to the "History vs. Hollywood History Channel Test" as it does "Time Bandits," "Baron Munchausen," "Moulin Rouge," or "Lord of the Rings."
They make movies off in their own bizarre little world, which is a perfectly valid way to make movies.