Well it's like with my parents. I told them, begged them, do not hit Tucker, please! And for the most part they have followed my wishes. But this also means they are completely incapable of teaching him any manners or working on him with any problem behaviors. In their mind hitting is the only way you can get rid of bad behaviors. What they see me doing to train him they consider complicated and too hard for them to do (not that they've ever listened to me try to explain what I'm doing).
I certainly agree all dogs, regardless of their background, need to be taught to live safely and harmoniously in our society, I just think I get why it's not always being done.
I also agree though, that you don't always know what people have been doing with their dog. If you walked by me and Tucker and he flipped out when he saw your dog you might think I'm "letting" him, that I have not been working with him on it. You'd be wrong. I am also known to say that some of his issues are genetic. I am not saying this to excuse the behavior, but so that people have an understanding of why he behaves the way he does. People who say their dogs problems are caused by their background may not be lying, and they may actually be working with those dogs to help make them better, but just want you to know WHY the dog is not "normal", especially in a world where certain behaviors (like my dog's aggression) are seen as the result of abuse (even though they are often not) or failed puppy raising, people want to make it clear it wasn't them who caused it, because no one wants to be seen as an animal abuser or cruddy dog owner.
But people who simply think training is cruel, even positive methods, are silly. It strikes me as a PETA mentality, they think "making" their dog work is wrong, requiring them to follow certain rules is wrong, slavery. Which wouldn't be a problem if their dog only ever saw or interacted with them, but that's not generally the case.