Yes, although he has saved many dog's lives, because sometimes he is their only hope, he really needs to understand that it actually hurts when you kick a dog in an unprotected area!
Either he has to not kick as hard, or maybe just even nudge with his knee (Cesar, if your reading this, noticed I said "nudged") or he should make these special things he puts on the back of his shoes, like something thick and padded, so it won't hurt the dog, but the dog feels it.
Also many people see Cesar "biting" a dog on the back of his neck with his fingers, and many people think it hurts the dog. Actually, (no, I am not supporting the kicking or the choking of the lead that Cesar also does) but dogs are really tough. Have you ever seen a 3 year old kid climbing all over my mastiff mix Sugar? (Picture is there <- ) and sometimes I even do it to my little sisters when they are hurting each other, and considering my sister cries if someone piffs a pillow at her really hard, it can't hurt a dog that much if my sister doesn't cry.
Its just a way to communicate to your dog that you don't agree with his/her behaviour!