Eh, I have seen a lot of trainers using a rope around the middle for 'bucking out' a horse. Here is clinton anderson using it.
I personally have no problem with it. Honestly where I stand I saw nothing horribly wrong with what the guy was doing. I don't like how often he gets jerked around by the rope that is on the flank, but honestly I don't think I, or anyone for that matter could have avoided it. Yes the horse was having a violent reaction, but for one this is a video to only show the horrible parts. I am looking this guy up now to find more proof one way or the other. Maybe the horse turned out to be a wonderful horse under his supervision, or maybe it turned into a monster. Can't judge by that video. I am always very slow to judge because I have seen tons of people confront horse training / sports and will base facts off of limited information.