Here is the Wikipedia page on Millan:
http://en.wikipedia.org/wiki/Cesar_Millan
And here is what his critics say according to this page:
There are professional trainers, behavior consultants and behaviourists that state that Millan's methods are inhumane, referring to the use of alpha rolls, flooding, and constant leash "corrections". According to them these techniques can have serious behavioral consequences. While critics agree that Millan does not hit or physically injure the dogs he is working with, they state that subjecting a dog to these techniques is inhumane treatment.
Dr. Nicholas Dodman, the director of the Animal Behavior Clinic at the Cummings School of Veterinary Medicine of Tufts University, has said ?Cesar Millan's methods are based on flooding and punishment. The results, though immediate, will be only transitory. His methods are misguided, outmoded, in some cases dangerous, and often inhumane. You would not want to be a dog under his sphere of influence. The sad thing is that the public does not recognize the error of his ways.? [15] In a February 23, 2006 New York Times article Dr. Dodman says of Millan?s show "My college thinks it is a travesty. We've written to National Geographic Channel and told them they have put dog training back 20 years." [4]
Jean Donaldson, The San Francisco SPCA Director of Academy for Dog Trainersstates, ?Practices such as physically confronting aggressive dogs and using of choke collars for fearful dogs are outrageous by even the most diluted dog training standards. A profession that has been making steady gains in its professionalism, technical sophistication and humane standards has been greatly set back. I have long been deeply troubled by the popularity of Mr. Millan as so many will emulate him. To co-opt a word like ?whispering? for arcane, violent and technically unsound practice is unconscionable.? [16]
Dr. Ian Dunbar, Director of the Center for Applied Animal Behavior in Berkeley says "He has nice dog skills, but from a scientific point of view, what he says is, well ... different," says Dunbar. "Heaven forbid if anyone else tries his methods, because a lot of what he does is not without danger." [17]
Dr. Andrew Luescher, Veterinary Behaviorist for the Animal Behavior Clinic at Purdue University says ?Millan's techniques are almost exclusively based on two techniques: flooding and positive punishment. In flooding, an animal is exposed to a fear (or aggression) evoking stimulus and prevented from leaving the situation, until it stops reacting. To take a human example: arachnophobia would be treated by locking a person into a closet, releasing hundreds of spiders into that closet, and keeping the door shut until the person stops reacting. The person might be cured by that, but also might be severely disturbed and would have gone through an excessive amount of stress. Flooding has therefore always been considered a risky and cruel method of treatment.? [18]
On September 6, 2006, The American Humane Association issued a press release condemning Millan's tactics as "inhumane, outdated, and improper" and called on The National Geographic Channel to cease airing the program immediately. [19]
Also in the month of October 2006, The Alaska SPCA refused to sponsor a dog rescue benefit by one of Millan?s trainers, stating "We just don't align ourselves with the Dog Whisperer's methods?. [20]
That's a lot of criticism from a lot of credible people and organizations.