Wrong. If your dog tries to attack others, there is immediate danger...at least to the dogs.
Putting a collar on a dog with spikes pointing in, is in my opinion, cruelty to animals and should result in the animal being taken away from the owner. Of course it will hurt the dog!
I think the idea is absolutely inexcusable and unacceptable.
Train the dog.
(PS - I'm not an animal rights type, but I have no sympathy for those who fail to train animals and instead come up with ways to injure them when they don't behave in ways they have not been trained to behave. I believe owners carry primary responsibility.)
While owners may carry primary responsibility, there are some instincts within dog breeds that you're going to be extraordinarily lucky if you can get the dog to to not do. Greyhounds are a great example, even if you don't get a non-retired racer, they'll still take off like a shot against some sort of coursing prey, like a rabbit or squirrel. Rottweilers usually will rarely bark. Jack Russell terriers won't ever sit down, and if you hooked them up to a treadmill 3 of them could probably power the entirety of Kansas and Nebraska.
I'm pretty good with dogs, and have been able to assert myself over most of the dogs I've encountered that have been owned by my friends or family, but one of my friends had a Siberian Husky mix, and despite years of training, that dog would still get into "pull mode" when you put the harness on it. Not to mention how it would try and assert itself as pack leader if you looked at it the wrong way.
You're free to act outraged at a perfectly valid and safe training aid all you want, but the pressure exerted by the pinch collars is really genuinely not anywhere near as much as you're probably thinking it is. Like I mentioned before most dog breeds have a lot of extra skin on and around their neck, and their skin in many cases is tough. When I play with my dogs, my arms will usually get quite scratched up, and that's just from them using their paws and claws. I don't want to imagine what would happen to my arm if they decided to use their teeth on me, like they do on each other, around each others' necks.