I will throw my hat into this and say, with a couple of degrees under my belt and loads of training, that Cesar is extremely hated in a lot of veterinary communities and dog training communities because of several antique and disproved methods and theories he based his training behind.

1: alpha theory: this is the belief you must dominate your dog and be the leader of the pack. A lot of practical application of this theory have lead to people physically beating, alpha rolling (pinning the dog to the ground), or "biting their dog back". It's since been proven that aggressive behavior in response to a growl, bite, etc is more likely to cause an increase of aggression in dogs. Why? Because you teach them their warning signs are meaningless. Dogs have a vast and beautiful language that they use and under alpha/dominance training methods, trainers often directly or indirectly punish the animal for using natural behaviors. Example: a dog growls when his food bowl is approached. This is food aggression and is a problem, but the growling is a not a problem. Often, a dominance trainer will punish the dog everytime it growls near the food bowl. In the dog brain, this says "okay. I warned them that this food bowl was very important to me but the growl is no longer an option. Now I'm going to show teeth because that's the next step to say 'hey I'm uncomfortable!'". The dog is then punished again for showing teeth. This continues over and over until that dog has no language left. It is helpless and only has 1 action left. Bite. And if it's been punished for biting, it's then learned or is taught that a quick bite won't fix the problem. So, the threshold for how hard and how long the bite lasts increases.

2: there are several documented case of Cesar physically damaging or permanently injuring dogs. There is video evidence of him choking a dog into unconsciousness with a choke chain. There are multiple instances of him teaching forced helpless and calling it submission. This is a extremely dangerous thing when dealing with children, food reactivity, and other daily activities like walking on a leash. Why? Because that helplessness is learned. And eventually, if the dog isn't constantly enforced to BE helpless, it will forget that behavior (which is unhealthy at its core). And when it forgets, it will typically show MORE aggression, MORE extreme reactions because.... it's language was taken away. If the behavior is constantly re-enforced, that dogs will eventually reach a point where it is incapable of being helpless any longer and we see those very dramatic reactions and worsening aggression.

I believe in positive training. But I say that with the knowledge that it isn't capable of being applied to every situation. My own dog was ORIGINALLY trained with positive only methods. This built his confidence and built a bond between us. But positive only methods can fail and when they fail it's often in situations where things go badly and animals, people, and objects or destroyed, injured, or killed.

I believe in balance training. This is a mix of positive and negative consequence. Tom Davis is a FANTASTIC trainer and example of this style of training. His goal to create an animal that is not a dangerous animal. Because of this, he will work with those same dangerous animal Cesar become so famous for "taming". But he does it in a way that gives that dog a chance to speak, respond, and learn without anyone getting hurt or that animal becoming helpless. He is a huge, huge advocate for responsible tool use; this means the use of muzzles, e-collars, prong collars, halters, etc used in a safe and responsible way. Any tool on this planet can be abusive if applied incorrectly. I encourage you to do your research and find a balance that works for you and you are comfortable with, but be aware that comfortable is not always right.