I belive natural horsemanship can help horses and people who have had a bad start, have been subjected to harsh methods, or have issues for other reasons. Could be that any training for a horse/person with ingrained issues will take longer because one has to start from a point further from the goal.
My experience with a Morgan trainer was absolutely horrifying, I hope Dan's was not. Nails under the shoes (to encourage them to pick up their feet smartly), ginger applied to the anus to hold their tails up, whips, riding with a section of garden hose instead of a crop for better response(because the horses had been beaten with one - they leave less bruising). Soring. Peppermints to hide the odor of drugs on their breath. The little kit of injectable drugs I would run across occasionally, the laughing reply of the need to pep up the old ones and calm down the young ones. I could go on.