After watching a few of his videos, reading his manifesto, and educating myself... I implore you to please please please pick up the book On Talking Terms with Dogs; Calming Signals. The dogs I witnessed in the videos are hot messes after he gets his hands on them and its a mighty shame. I don't think dogs need to be taught using fear. I do believe that dogs should not be pushed over their thresholds and become stressed, training should be upbeat and super duper fun.
Quick go over of what I saw watching his videos: One was a couple of obese labs. When he put one into a down the dog had its eye whites showing and was purposefully looking away licking its nose and lips with its head down; these are signs of stress and to pacify what is stressing them. Another video was a dog aggressive terrier. Don got the dog to meet and greet with another dog and the body language again was pretty bad; head down, eye whites, stiff, purposefully looking away in avoidance of the situation. Third was a REALLY hard correction on a GSD who then cowered and... started practicing avoidance behaviors.
Just for comparison, these are the same situations trained differently:
https://www.youtube.com/watch?v=S00jB7jmKic teaching a down with a lab. Loose loose body language, waging tail, trying different things to earn the reward. (She's clicking for looking down or any movement downwards).
https://www.youtube.com/watch?v=Vk4PPcE1CqY down stay. Its long so you can fast forward or whatever. The dogs are once again loose and happyhappy.
https://www.youtube.com/watch?v=xf3Q6x__Xbg dog aggression. The dog is still pretty darn loose, happy, focusing on the trainer and actually making decisions on how to behave.
Now, its important to know, though, that calming signals are completely natural in the dog world and are typically respected amoungst the dogs. Dogs moving through something typically exhibit calming signals as they try to choose an alternative behavior to the one they are offering ( A leash reactive dog confronting another dog and then working through the situation, for example). What I don't like is a human being forceful or persistent enough to actually push a dog into offering calming signals, people should be dogs advocates and calming signals should never fully be directed at the one training them.
https://www.youtube.com/watch?v=A_7dl4c-IrM A video show casing calming signals used amoungst groups of dogs.