To quote from the commentary directly:

"It's simply a fact, you know, that this happened, I mean, there was like kind of extremely young kids in the war effort and there's also like kind of this moment where like kind of you have to... you have to, where he has to, the character has to kind of like make this moral decision, now he's only kind of set on kind of like kind of trying to kind of rescue his son and, uh, he knows that he, in a way, he has to kind of do everything you know to get his son, and one kind of choice is to give his, uh, kids like guns to try to help him distract, you know, the soldiers from him while he, you know, so it's more possible for him to kind of like kind of save him."

This quote, pulled from Roland Emmerich's commentary on The Patriot is symptomatic of what's wrong with many "blockbuster" directors these days. If there's any subtext or social commentary in the movie at all (as there can be even in big-budget filmmaking), it's because it was in the script and is a natural side-effect of simply transferring the material to the screen. Directors like Emmerich, DeBont, Harlin and others seem completely oblivious to anything deeper than the cool imagery they're capable of splashing across the screen. These guys can make a movie LOOK great, but it's doubtful they truly understand what it is they've created. Hope they don't consider themselves auteurs in anything other than style.

In fact, I've read in more than one source that The Patriot was more of a reflection of Mel Gibson's politics than anything, which means there IS a political statement to the film, but I'd bet Emmerich's commentary pays it no mind because he's blind to it.