I completely agree with Cesar Milans type of training. BUT it has to be applied correctly and to the right dog. It's about knowing each dogs personality. I used this type of method with my rottie and she was a wonderful dog. But, on the flip side, I helped with a greyhound rescue a few years back and those retired dogs were already so timid that any type of firmness could send them into their shell.
The pack leader theory has not been debunked. There are just newer theories and people who disagree and prefer a more positive approach to training. Which is fine. I tend to think people humanize dogs and think that being alpha hurts their feelings. It doesn't. Dogs crave leadership and control (in the right way). Now, I do not support abuse, hitting, yelling, aggressiveness at all. But i have helped train dogs for years, I have attended classes and researched all types of training...including positive approach training. And for the most part I see better results and agree with cesar Milan type training, or pack leader training.