I don't believe it is wrong to kill a dog that has attacked a human, further there are laws that put responsibility back to the owner (if there is one) to pay for damage/costs incurred as a result of their dogs actions. If taken through court, the owner can be fined and the court can order the destruction of the animal. Law enforcement agencies here (northern territory australia) have the legislated power to destroy dogs on the spot if that is deemed the most appropriate course of action.
Euthanising dogs can be an act of a responsible owner, an option taken by law enforcement or a necessary part of veterinary work, where an animal is beyond help and it is used to end suffering, I don't think murder comes into it.
So called "forced" neutering of dogs is a good thing in communities where the dog population is quite large and causing health problems. Preferably, before this happens, there would be responsible owners who would neuter their animals if they do not intend to breed from them.
I agree that there are intelligent animals on the planet and that some of them require and need legislated protection to ensure their survival in the wild and put forward offences/penalties for people who would seek to profit from the destruction/exploitation of these creatures.
I don't agree that dogs should be put in this same category. Where a dog is outside its property, if it causes trouble menacing people, chasing cars, worrying stock etc. then the owner of the dog gets a chance to take better control of their animal. If the dog attacks someone or does any troubling/menacing behaviour for a second time, the appropriate action is to destroy the animal. (landowners can control dangerous/nuisance dogs on their property by shooting or trapping if they wish)
It may seem harsh, but in areas where there are no dog control laws (such as where I live), it is a simple and effective means of controlling dangerous dogs.