My family was in upstate NY before and after Saratoga, served in the NY Militia, it was very nasty, and was nasty for quite awhile.
. The war in the south was pretty brutal, and more of a civil war, which I think the Patriot portrays pretty well.
The one scene I objected to was where the British burned the church full of people - that was based on a true incident where a barn full of horses was burned alive by Tarleton. There was no need to exaggerate imo.There were atrocities aplenty.
The movie might interest your son enough to read up on the Revolutionary War in the south - I know my 8th grade son and I really enjoyed reading about Francis Marion, Nathaniel Greene, and especially Daniel Morgan, the teamster turned general, who won the Battle of Cowpens, the battle depicted in The Patriot.
Read the book, "A Devil of a Whipping" describing his exploits and your son will come away with a stirring pride for what our American soldiers pulled off.