It's never entirely one or the other. I have a dog who has had fantastic nurture all his life. He is a very spoiled dog. When he began showing signs of aggression, it took me months to change the bias I had, which matched your comment perfectly. I absolutely believed what you write here. Now I know better. I adore our dog, but his nature is strong, and he is a natural guard. His nature divides the world into "in group" and "out group" and he treats those two groups profoundly differently. He absolutely views his purpose in life as protecting those of us within his pack from those of "them" outside his pack. When we intend to have people/dogs spend time with him, we have to do so carefully, giving him lots of monitored time with them in a controlled situation so that he can adjust to the concept that these people/dogs are a safe part of his world. Until he accepts them in that role, he reacts with "the best defense is a good offense". Once he accepts them into his world, he is the sweetest marshmallow in the world. It's quite a dramatic dichotomy.

When a dog enters my life, the first priority is to socialize and train the dog. I'm quite dedicated to this. I put a lifetime of work into learning to communicate (two-way) with any animal who lives in our space. This isn't a question just of good will. I put work and discipline (almost all positive training, unless there is absolutely no way to train an element without a negative stimulus) into developing the dog's ability to respond to what we wish them to know. Living with a dog is a relationship, and the dog must completely understand our expectations while simultaneously being 100% sure that we are a trustworthy, safe friend that they can depend upon absolutely for their safety.

I used to have two labs. They were easy. They loved everyone equally. They were goofballs. I also had them from puppy to the end of their lives. The difference between them and our pup now (herding dog mix) is dramatic.

Our pup now is supremely responsive to us. As his pack, he listens to us and pays attention to what we tell him in a way that is frankly stunning. For example, today I was out walking him (he was off-leash, as there was nobody within half a mile and I had clear visual sight-lines for hundreds of yards in all directions) and he picked up a dead mole he found. I'm still shocked because I realized within seconds what he had and I commanded him to drop it. Damned if he didn't drop it! With a prize like that (a yummy smelly relatively fresh dead animal), this is no small thing. He wanted that mole. But he dropped it when I told him to. That's the level of response he offers us as his pack. He listens to us and is absolutely always paying attention to us. He is completely safe off-leash (as long as there's no perceived threat) because he has an absolute desire to stay with his pack and operate with us. He centers all his exploration in a circle of maximum 100 yards of us, always coming back to check on us at least every 90 seconds. In other words, he's a herding dog. He operates in a circle around his "shepherd" (which is us).

What will overwhelm that instinct he has to respond to us is the even stronger instinct he has to protect the herd. If he develops a sense that some space (his home or another place he considers "his") is to be guarded, then anything that comes within his perimeter must be driven away, or if it doesn't go away and approaches, it must be attacked. This is an absolute mandate within his nature. Commands at that point bounce off him like a brick wall. He hears nothing except his interior mandate to "deal with the invader". Until the threat is neutralized, his action is independent. He knows what he needs to do, and he shows zero need for input from us.

Because of this, as I said in my comment above in the thread, we now know that our job is to control his environment absolutely. As long as he is in a controlled and safe environment, he is literally the sweetest dog you can imagine. He is sweeter and more affectionate even that my labs were (and that's saying something!). He adores us and anyone within his perimeter. He would be radically incapable of conceiving of the idea of harming anyone within his pack. No matter what we do with him (we could actually cause him physical harm), he trusts us 100%. There is no greater trust I have of anyone or anything in the world than I have for my pup, with relation to me or those in his pack.

It's quite remarkable actually to see the clear demarcation of "in group" and "out group" that is genetically coded into his nature.

As I said, before this pup, I didn't know everything I have written here. I believed just as you said that it's all about nurture, not nature. I have now learned otherwise. Do not ignore the nature of an animal. It is real, and to live happily with that animal and to give that animal the happy life we wish to give them, our training and the structure of the life we design around the animal must take the nature of the animal into account. Because we know our pup's nature, we give him what he needs, and he remains the happiest and most spoiled pup ever. But if we were to try to pretend he is capable of overcoming an instinct as strong as his "guarding" instinct is, we'd be doing both him and ourselves a disservice.

There's a reason there are animals that cannot be safely domesticated. There is no such thing as a "safe" wolf, no matter whether raised from the youngest puppyhood in a happy human environment. Genetics cannot be ignored; those animals are not programmed to live in human society, and they are unable to submit their instincts to our requirements.

Dogs fall on a spectrum between the wild untameable wolves, and the goofy lovable goldens. The best, most flexible dog-companions must be aware of these differences to be able to adjust our expectations depending on what each individual animal requires for our and their own happiness.