It's the same as with any piece of equipment... It's dangerous with the wrong people using it. Haltis, gentle leaders and the like can be perfectly safe if the handler knows what they are doing. The danger comes clear when people give corrections on the head collars, like when walking and the dog surges forward, instead of the handler letting the dog reach the end of the lead (which is what loose lead/social walking is all about), the handler yanks on the lead to try to tell the dog off. It can severely damage a dogs neck when it gets snapped around like that. It's all because people have a lack of education.
The only type of harness that I have found to be effective with pulling dogs is front attaching harnesses, the other types encourage pulling because it makes it more comfortable for the dog.
The issue with that is that in most cases there are lots of different tools and techniques that will work for each situation. But in SOME (not all cases) by the right person, a prong collar can be the most effective and lowest stress option for the dog. If something that can be cured by 3 small corrections with a prong collar compared to a combination of 20 time outs, multiple correction chain corrections and other methods.... I know which one the dog will prefer. It's not that there aren't other ways of doing it, sometimes it's just the best way of doing it.
I have used (where possible) all dog training equipment on myself before using it on my dogs. (Even a bark collar!) I must say that despite it's appearance the Prong Collar had a nicer feel compared with the Correction chain. The correction chain gave a severe jolt and bruising. The prong collar gave me no injuries but I had no will to resist because it was very unpleasant. Forgive me if I am wrong but isn't that the point of a consequence!!
It seems to me that most of the people with a negative opinion of prong collars haven't actually tried one or researched up on them in a non biased manner. Also most of the people against them seem to have dogs without any major behavioural problems and just seem to be basing their opinion on the look of them or what they have heard other people say. That annoys me because my research of prong collars suggests that they can be very effective with particular dogs and with difficult behavioural problems that haven't responded to other interventions. When used properly Prong collars seem to actually be better than other interventions in terms of effectiveness and in limiting distress to the dog. I think peoples opinions are based on politics and about judging others unnecessarily and not what is in the best interest of the dog. I have a dog who is half blue heeler and half staffy and she came to me from a puppy farm with A LOT of problems. I have been able to help her with so many of her problems but after 3 years she still has problems when she sees other dogs and barks and lunges at them. Even after seeing 3 different trainers and taking her to dog training I have not come up with a good solution for her. Positive reinforcement has not worked with this issue and it is stressful to walk her. Before getting her I took my other dog for a walk every single day but over time now that i have my second dog (who has these problems), the walks have become less and less. My dog who has the problems is a very strong willed dog. She is also physically strong. She once climbed our fence on the balcony and jumped a whole story to the ground and then just got up and walked off as if nothing had happened. I pulled up in my car and saw the whole thing happen. I have not used a prong collar on my dog because I am in Victoria and it is illegal but I think my dog would actually benefit from one. Regardless I would like to have the choice to try it and as a conscientious owner I would never use it to hurt her just to help her gain confidence around other dogs and only for as long as necessary. I really doubt that most people would go around using a prong collar just to inflict harm on their dog. If they did, then I doubt that banning the prong collar is going to stop someone like that from hurting their dog using some other method. Maybe we should also ban flat collars because they can be used by unscrupulous people to choke a dog or dog bowls for that matter because people can hit dogs over the head with them to abuse them. I think prong collars should be allowed if the person has exhausted other avenues and is given proper training to use them. Blanket banning them is just politics and taking away options from good owners who actually love their dogs.