Some parts of this video are terrible, but the majority of it is not. Even the most domesticated dogs will bite and attack strangers - this is very common at vet clinics and boarding centers. Binding the teeth is often required when administering treatments or just giving them a bath. Using a leash with a knot is just amateur and lazy - they should have used a proper muzzel, which is something that when used properly is fully endorsed as a restraining device to protect vets and caretakers.

Pulling on a 'choke chain' is a confirmed training technique that doesn't harm dogs. It's how they learn. Alpha dogs will bite down on necks not to cause pain, but to establish ownership of that dog's neck. In the first clip, it is being used correctly and that dog is not being harmed. It is being heeled.

Poking a dog with a broom? yeah I got nothing for that. That's terrible. Dogs in "cages"? Those are called pens. You can buy them at Petco. Using them is not abuse any more than drinking a beer is illegal. It's what you choose to do AFTERWARDS that can sometimes be illegal.

source: vet tech for 15 years