By most accounts it was the episode about Kane, the 2-year-old Great Dane with an irrational fear of linoleum floors, that incited the dog world. Trembling and drooling, the 160-lb. dog was commanded by Cesar Millan, TV's Dog Whisperer, to walk along a hallway until he appeared, to use one of Millan's favorite terms, "calm-submissive." But soon a dogfight ensued over Millan's methods: In one hurtful comment, a prominent veterinarian from Tufts University's Animal Behavior Clinic accused Millan of "setting dog training back by 20 years." "I was upset," Millan says. "Jada Pinkett left me a message: 'Just remember we love you, we believe in you. Stay strong. You're the man.'"

That much isn't in doubt: Now in its third season, Millan's Emmy-nominated Dog Whisperer is the highest-rated series on the National Geographic Channel, and its Mexican-born host—who, with no formal training, launched a career taming the wayward pets of Hollywood stars—is arguably America's most famous dog handler.

But in addition to a rabid following, there are howling critics. Kane, it turns out, is no longer afraid of the floor. "He's completely over the whole thing," says owner Marina Dahlen, a Pasadena teacher, of the animal's 2004 appearance on Millan's show. But many dog experts aren't. In September—citing a technique used by Millan commonly called "flooding" (in which a dog is forced to confront something that he fears), his use of shock collars and his habit of pinning down disobedient dogs to establish mastery—the American Humane Association sent an urgent request to National Geographic to pull Whisperer off the air. "Some of his methods are outdated and even cruel," says Marie Wheatley, the group's president. "Unfortunately a lot of uninformed viewers assume that he's right."

At the heart of the matter is a philosophical disagreement. Says Ian Dunbar, a veteran San Francisco dog trainer: "It's become a huge emotional debate. Do you show the dog what's right [by rewarding good behavior], or do you punish the dog for breaking rules he didn't know existed?" Although Millan often works with aggressive animals—and despite the fact that his show begins with a "don't try this at home" warning—Whisperer-inspired handling techniques are catching on with owners of ordinary dogs in need of nothing more than standard obedience training, say the critics. Manhattan trainer Andrea Arden recalls seeing a man pin a stranger's Boston terrier to the ground after it growled at his own dog. "He then grabbed his dog and shoved its nose into the other dog's rear," she says. "He said he was teaching the other dog to be calm-submissive. He said, 'I am a follower of Cesar Millan.'"

But Millan—whose mantra is "exercise, discipline, affection, in that order"—makes no apologies for his remarkable ability to calm animals. "This is not a 'Sit down, stay, come here, good boy' show," he tells PEOPLE. "I'm the last hope for the people I work with. In the hands of other professionals, these dogs would be put down or on medication." Millan is in the process of moving his Dog Psychology Center from cramped quarters in South Central Los Angeles to a 42-acre spread in Santa Clarita. "I know I'm helping dogs," he says. "If I have to go against unstable humans, so be it."

According to National Geographic's director of programming, John Ford, the network is in talks with the Humane Association about offering another dog-training show in addition to Millan's. But Cesar's diehard fans are still whistling his tune. Singer Patti LaBelle, who sent her aggressive South African mastiff, Nasir, to spend a week with Millan's pack of dogs in L.A., has her own theory about Millan's detractors: "Jealousy," she says. "People are very judgmental; they do not like success." As for Nasir, "he came home a different dog," says LaBelle. "Cesar's a miracle man."