Olive Stone's movie JFK caused such a ruckus that there is a section on it's wikipedia page entitled “legislative impact”. Rewatching JFK now, it's fascinating to think of this movie having fooled anyone, because it's obviously full of sleight of hand and over-jumped conclusions. Stylistically, it's clear that Stone is trying to gimmick the audience – shooting certain scenes with hand held cameras so they will look like documentary footage, splicing actual news footage and audio in with his staged recreations to make them look like they are of a piece, omitting perspectives that would undercut his theories – so even if you are sympathetic to him at the beginning of the film it becomes hard to believe his narrative as the story unfolds.
But leaving aside all of the flash – which is well within Stone's rights to use as an entertainer – a lot of what he's trying to argue makes no sense at all. Stone's entry point into the JFK Assassination is New Orleans district attorney Jim Garrison, who put a man named Clay Shaw on trial as an accessory to the murder. The problem is that Garrison's case against Shaw is so insane it should never have gone to court. It basically amounts to “a gay man in prison told me that he had been to sex parties at Shaw's house, and Lee Harvey Oswald was also hanging around those parties, as were some crazy gun-nut Cubans, so clearly Oswald wasn't the lone shooter, but was part of a conspiracy with some other orgy-goers.” Leaving aside the hearsay nature of the story, leaving aside the high potential for bias with the one witness he has, leaving aside a lot of other legitimate legal problems that should have gotten this case thrown out of court... The problem with making this angle on the assassination the drive of the film is that it is at best tangential to the actual assassination since no one ever accused Shaw of shooting Kennedy, just maybe knowing some people who maybe had a motive to maybe shoot Kennedy. Therefore, the infamous long “back and to the left” scene in the court where Garrison keeps showing the Zapruder film over and over again and analyzing exactly how and when Kennedy got shot is like putting someone on trial for getting into a fistfight at a Chuck E Cheese and then devoting twenty minutes of your argument to analyzing a video of a rat eating pizza in a dumpster. I get how it thematically applies, but it also isn't particularly relevant to the question at hand.
Furthermore, the conspiracy angle of “Shaw knew x,y, and z people, all of whom had a reason to hate Kennedy” is a weak place to start an investigation. Any “who had a motive?” investigation is slightly suspect anyway because having a motive doesn't mean that you acted on that motive, but to do so with the death of one of the most powerful people on the planet leads down a lot of unhelpful rabbit holes. JFK made decisions that upset the Cubans, the Russians, the mafia, and so on, and all of those people could have been working together or some of them were working together or maybe it was just one faction. Stone can't really say which one of them he wants to finger because all are equally probable. They can't have all done it. He's clearly implicating everyone and no one and how is that helpful?
My guess is that Stone was less interested in selling a single coherent hypothesis for who shot JFK as he was in discrediting the lone gunman theory. Providing a lot of previously undiscussed possibilities shows all of the different ways in which 'evidence' was ignored to provide a simpler, cleaner story to the public at large goes a long way towards discredting the original story. Of course, having alternative possibilities doesn't make any of them true or the main narrative false, but it does suggest that the government wasn't telling the whole truth. To that extent, it sounds like Stone's film did achieve this goal, because it seemed like there was a surging distrust of the official story in the years after the movie came out.
Still, while I don't really believe a single thing I heard in this movie I can't say it was dull. Stone really commits to the crazy, which is entertaining in it's own way, and all the razzle dazzle he's throwing out as a distraction keeps things moving. If you're gullible it's probably better to stay away, but if you can just appreciate it as a movie then you'll probably enjoy it, despite it's long run time.