You should reread the post I wrote, and you quoted, because it's literally the first sentence.
I think vets should make that decision. They're the ones who would be performing the surgery and are hopefully ethically motivated towards the well-being of the animal. They should ask the right questions in order to determine cause of behavior and what action(s) the owners took before pursuing declawing.
The OP stated outright that the vets he took the cat to viewed the surgery as a better last-measure alternative to euthanasia. Obviously not everyone here agrees, but I agree with that point of view, even if I would not declaw/debark/crop an animal myself, under any circumstances.