I think that there can never be a historical movie that is totally accurate, simply because what we accept as history today becomes inaccurate next week, when new facts are discovered. It took more than a century for us to realize that Custer and his men didn't die heroically at the Little Big Horn, the American Civil War wasn't entirely, and some might even argue, mainly, about the issue of slavery, and that there were actually just as many colonists in North America who wanted to remain loyal to England as there were who wanted their independence. History is only accurate until some other diary, journal, or scroll is discovered and accepted as being accurate. Today's hero becomes tomorrow's villain, and today's war for freedom becomes tomorrow's political plot to place a new tyrant in power.
But "The Patriot" is a great movie, accurate or not. One of my favorites.