It looks like the GF knew the relationship was in the dumps and set him up.
Okay...I saw nothing "brutal." The guy's actions are pretty much what you would have to do to establish dominance, as has already been mentioned. Grabbing by the scruff is what the K-9 mother will do to her pups. This puts the dog in an inferior position, so the dog knows he/she is not the boss, and the owner is. Also, the dog being placed on its back puts it in a compromising position as well. Make the dog feel like it is the less dominant of the two. Think like a dog and you should get results. These methods work with my 86 pound Doberman.
That having been said, this owner needs to attend some EAP/anger management classes. If this tape were referred to the sheriff/police chief he most likely (and should) be referred to EAP. I would also like to know what type of complaint record he has on his department.
"...the men under your command deserve your leadership."-OXCOPS