PBS? I think they were showing it on TBS yesterday... you are referring to the one with Mel Gibson playing Benjamin Martin, right?
If so, I don't know how authentic it is, nor do I care. I love that movie, it is one of my all-time favorites. In fact, I watched it on DVD this weekend for about the 50th time. Great movie.
I'm sure, just like every other Hollywood interpretation of history, that liberties were taken. We've even discussed this particular film before... the church-burning scene, Gibson's lack of use of the loading block around his neck, Col. Tavington tossing ramrods across the battlefield like they grew on trees... even with the little things like that, I still think it's a great movie.