I do not believe he used his hands as I would have but it certainly isn't what I call "abuse".
Hell I could probably watch every rider at the World Equestrian Games and find SOMETHING I could bitch incessantly about. Then I could post a video about it on a forum if I wanted so everyone else could bitch about it with me! Then suddenly that rider becomes unpopular with a whole bunch of pixel people and is dubbed 'abusive'. (OP, not saying you're complaining, just bringing up a point)
When you guys were learning to ride your sport how many things did you do wrong? Were you all born winners? Were you all born with the infinite knowledge of how EXACTLY to use your hands and when exactly to use them? Were you all instantly good at developing a horse up into the bridle? If you say you were then you're lying.
I don't believe this man uses his hands perfectly but it is not abusive. The horse's mouth isn't bleeding, his jaw didn't detach from his face, his neck didn't break, and I bet none of his teeth fell out either!