I just don't believe a dog that is not ill can't be made normal
That's nice. Once a dog comes here it's usually bitten at least once and sometimes multiple times. If I adopt a dog out knowing that history, and the dog seriously injures someone, that's my fault.
I can't just hope something will happen if I believe it to be real. Faith won't turn an aggressive, kid-hating dog that kills cats and chickens into a lovable family pet. I've got to have a real, point-by-point game plan and facts to point to, and a strategy for the future management of such a dog out of my care, so that if something goes wrong (and so far so good), we can go over the facts again and see whether it was a preventable event. I can say, "If X happens, CALL ME, and we will go from there." X will not be a bite, but rather some subtle sign of reversion.
Almost all aggression boils down to preventable events. As Anne said, training and management can step in and sometimes dogs can be 100% turned around. Sometimes they can come back 50%, and I've got outlets for those. Sometimes 25% is enough if their aggression pattern is highly predictable, and I can place them with professionals. Corrie Dhu was one of those, to pick a recent example.
Other dogs have the canine equivalent of mental illness. If I were an owner and not a trainer on a limited budget, with limited space (yes, sadly it comes down to that), I might be able to "save them all." There's a couple of refuges I trust to take dogs that are nice, "but" - can't be trusted around people that aren't professionals. They love to work with me because the dogs I send are fully trained and often do tricks and whatnot - they are real ambassadors for the value of such places.
I know there are people who disagree with me, but I do believe euthanasia has its place in behavioral rehab. If a dog had a painful condition that would doom it to a lifetime of isolation, confined movement, and the only people he or she ever met other than vets and the owner, met the dog with fear and loathing, one would surely begin to entertain the idea of releasing such a dog from its suffering. If I've done all I can and still the dog will be doomed to a lifetime of fear and distrust, not to mention its own confusion and dealing with whatever drives or illnesses are creating the aggression - it's time to visit the idea of euthanasia.
I've euthanized about half a dozen dogs in my lifetime. One was fear aggressive to the point where he wouldn't let people in his kennel, or eat, and was starving himself to death. To move him from one point to the other we had to have a vet dart him. I hope I never see something like that again. He was line bred three times on a known fear aggressive dog. One was so aggressive towards children that he tore two kennels apart trying to get at my kids, after he arrived. If he was on a leash and saw a child, he'd go up the leash and bite YOU trying to get you to release him. I worked with him for about two weeks and then had to let him go.
The other four had a seizure disorder somewhat common among Border Collies, males between 2 and 3 years old. It's idiopathic in nature and manifests as random acts of violence (no pattern). Mixed breeds seem even more subject to this for some reason - two of the ones I worked with were mixes (one with cocker spaniel and the other with collie, known mixes). Nicholas Dodman did some work in this area about ten years ago. He had mixed results treating with pheno, but when one of these makes it into rescue, we can't take a chance that the aggression will return in the future, as it often does.
A seventh dog was a female who started out very aggressive, seemed to improve after about six months of work, then after coming down with ehrlichia at the herding trainer's home, became extremely and randomly aggressive, as well as experiencing some minor seizures on a regular basis. The vets assume that the tick disease brought about the same brain changes as in the above dogs, but caused by the disease. I had a nice old dog who came to me with tick disease and developed pheno-responsive epilepsy, so I knew that could happen.
I believe you can start out assuming that this one can be saved. But I don't think it helps me in what I do to think, They must all live - in whatever life that means. Being saved is sometimes a distinct concept to me, from being alive just because it makes me feel better about myself.
We had to dart and sedate that fear aggressive dog, just to get me and the vet in there safely. I had set it up before this dog arrived, so I could slide my scooper under the bottom of the kennel panel and change the shavings, so they were clean enough to lay in. For about ten minutes, while the vet and tech got set up, I held that dogs head. I'll never forget the transformation that came over his face as the drugs relaxed his brain - for the first time he could really see things without the haze of fear, enjoy the feeling of hands that weren't rough. Then the doctor gave him the final injection. He sighed and closed his eyes (something I'd never ever seen him do) - and he'll never know fear again.
And he'll live forever in my memory as that dog - not the victim of bad breeding who seriously injured two children on separate occasions, plus another professional trainer - but instead he is the one with the brilliant, soft eyes, and clever face, who enjoyed that last minute of stroking.