As cheap as they are these days, none of us should be without a little video camera of some sort when we hunt. Probably you only get footage of the retriever doing his job, but it could really come in handy in this sort of situation. I had a road rage incident once that was instantly quelled when I pointed my camera in the guy's direction. A case like this hinges on whether he was trying to scare birds away or hunters away, and if it was the latter, I want them to throw the book at him. If it's the former, well, I want them to throw that book at him too, but yeah it's an admittedly lighter book
"We have met the enemy, and he is us."
Walt Kelly, via Slow's avatar. Look it up