Ceasar Millan is a bit too aggresive in my eyes, but the basics of his interaction with animals really helpfull. I have great bounds with dogs, cats and horses before I've ever heard from him. They always like to be near me (just like most people because of my calm energy) and respect me like I'm one of them. The only dogs that are aggresive towards me are spoiled ones. They don't know how to react on "strange" things and are just like raphjd said either afraid or overly pampered. Ceasar only opened my eyes of how your emotions and attitude affect others (animals and people). In this way I've already helped 4 dogs overcome their issues in just using my voice, attitude and a few times a small push/"bite" to snap them out of their obsession.
Most people find the last not right and find it animal cruelty. I know my own strength because of practicing martial arts and if you hurt an animal they will react on it. (I know because I've stepped on a dogs foot once while walking backwards. He bit me lightly as a warning so no blood or anything else happened and he was just fine.)