PP is the most important for people who are endangered by other people or who already were endangered and that is why they feel the need of having a good protection dog.
If someone desires a good protection dog, then by all means, go ahead and train for it. But PP is never the most important thing to train for, even in dogs that are intended for PP, basic obedience and early socialization is necessary.
I think that owner's job to protect his dog(s) is only valid if he has weak and companion dogs, not utility ones.
It is always the owner's job to protect his dog. Even police k9 officers take precautions to protect their dog whenever possible.
Everything depends on the purpose of your dog, which can be to have a good companion and friend as well.
Regardless of the purpose, all dogs should be trained in basic obedience and socialized.
I agree that the majority of people I will meet with my dog are good people, but now and then we will also meet some bad guys. And how can my dog recognize bad guys among all the good? Better is to let the dog distrust anyone. That is my opinion.
It's the owner's job to determine a threat. Many dogs can recognize a perceived threat without being specifically taught. The owner needs to be able to override that when the dog is in error. That is done through obedience training. Socializing allows the dog to accept friendly strangers.
Protection training teaches the dog to act on cue as well as teaching the dog to automatically respond to a threat (good guy/bad guy).
If I meet a friend on the street who is unknown to my dog, I don't want my dog alerting or biting. If I take my dog to the vet or need to board him, I need him to be handled by the staff. If I get sick, I need my dogs to allow someone else to care for them.
A well trained PP dog will alert to a perceived threat, will guard and bite on a command, will stop alerting and stop guarding and stop biting on command, and will allow friendly strangers to approach him.