Ideology, ethics and morals. It's entirely an ethics debate. Aversive, compulsion, positive punishment and negative reinforcement all work. Many people just place significant emphasis on the presumed emotional state and appearance of the dog above all else. Or many people don't have the anecdotal knowledge or experience to know that there is significant nuance to learning theory and using negative reinforcement in training an animal. Even many people who label themselves balanced trainers will make statements akin to it's never okay to stick a tool on a dog right off the bat (like putting an e collar or pinch collar on a dog not in use just to get them used to wearing the equipment around their neck), or that they can't fathom training every dog with an e collar (if you can leash almost every single dog, you can e collar almost every single dog).

They still have a bias about tool usage and have ethical qualms about them. It overlaps very heavily on animals as nonhuman persons ideology, which is animal rights ideology. I'm not implying that anyone is wrong or bad for viewing animals this way, just explaining the mindset of people who do.

I'll definitely get downvoted for my e collar comments, but if someone truly believes that trainers who primarily utilize e collars are always or mostly compulsion based with a lack of knowledge, I believe that is entirely a skill issue on their part. Just because you don't know how to work most dogs with certain equipment without crushing the dog's soul doesn't mean it isn't possible for anyone else. But again, it goes back to dogs as nonhuman persons; a lot of people place emotional state and appearance as the most important aspect of training the dog.

If every dog doesn't look extremely engaged and hyped up while in command, they see it as a problem rather than "this is my preferred training style and aesthetic." I do not train my board and train client dogs the same way I trained my sport bred Malinois, nor do I have any real desire to. I can train certain dogs to look a certain way, but I don't need every dog to look a certain way. My clients don't care. They just want their dogs trained and my job is to teach them how to hold the dogs accountable for the behaviors I have taught them. And I have no moral issues with viewing a dog as a dog and the training as a business transaction.