Saints fan here. As if you can't already tell from my screen name
I watched the replayed probably a dozen time by now. Initially, I thought it was a bad call. But after a few times in slow motion, I noticed Brooks' right arm wrapped around Brees' neck which some may considered that a clothline, which in turn is an obvious penalty. In addition, Brees was bleeding from the mouth. Mike Periera also thought that was the right call.
P.S. Your D played one heck of a game.