I have not read all of the responses but I did watch the clip several times.
I don't see a mad horse at all. I see a horse trying to do the best he can.
I don't see a horse that is going to hurt himself at all. If this were the case, no horse would be able to run the barrels. They would all be crippled. They not only do this, they do it at high speed.
I do see a horse that is crossfiring and unable to canter a tight circle correctly.
We do this all of the time but with a stock saddle. We gradually draw down circles paying a lot of attention to the horse staying in lead. We pay great attention to keeping the horse's hip over to the inside.
This is a great exercise in teaching body and hip control. It helps a horse learn to bring that inside hind leg up for quick turns in the pasture while working cattle or any other time quick turns are needed. Until a horse learns to bring that inside leg up underneath him, he is very prone to falling when he tries to turn fast while going forward to get a cow back where it belongs or ???.
We have often thought how close this is to a pirouette once the horse learns to keep that hip in and hind foot forward.
We have worked with a lot of barrel racers that were having problem. One of the biggest problems they have is a horse that throws its butt out as it turns the barrel. If you watch any barrel racing competition, you will see that at lower levels many horses are doing this. You watch very high level competitions and you see very few horses doing this and they are all beaten by the horses that keep that lead behind until they need to change leads completely, front and back. So, this is the exercise we start with when he help these riders.
One big problem is that when a horse has learned to throw their butt out and crossfire on a tight turn, it can become a real bad habit that is very hard to break. So as you add speed, they go right back to doing it. For this reason, it is very important to do this gradually and try to keep horses correct.