It isn't even a question of "would we ever say?", at least in this instance. There are groups of people that actually already make this argument.
Indeed there are, which personally I find a very difficult ethical road to go down. The argument is essentially we should let them exist in their natural state, but whilst I would agree in terms of wildlife that presupposes the existence of a concept which is doubtful at best.
"Nature" no longer exists for most of these animals, if indeed it ever did. Going back to my German Shepherd analogy in nature no such beast exists, they have been selected for by human intervention. Left to nature my GS would be a wolf, prowling the woods as part of a predatory pack. Human intervention over the millenia successively tamed the wolf then bred to select for traits which were desirable, reducing the aggression, molding the pack instinct to incorporate people rather than other wolves and favouring ever larger, stronger, but ultimately less efficient forms.
The end result is an animal which is no longer suited to the natural environment, an animal which essentially exists, can only exist, in a state of symbiosis with humans. They seek out humans to bond with, they are born with the instinct to do this. When they are employed as guard dogs, police dogs, seeing dogs for the blind, they are following an imperative they no longer have a viable alternative to. They are dependent on us for a rich diet they would be ill suited to finding for themselves in a world where they would no longer be able to hunt anyway. They now need us.
We could debate the ethics of creating such a situation but in the case of most of the animals being employed in such a manner that boat has sailed, the "damage" (if damage it is) has long since been done and is out of our control. All we can do is make decisions about how we handle the end results.
When I refer to police and seeing dogs being "employed" this isn't a casual choice of words. They aren't being used, there is a two way relationship where they willingly provide a service and receive reimbursement. Our police colleagues may weigh in here but I'm pretty sure their dogs have fairly extensive employee rights which include breaks, health and safety regulations, age based retirement, protections against illness and injury in the line of duty. It isn't callous and we've treated human employees far worse in the past.
I don't for a second buy the idea that my dog doesn't understand the idea that he and I look after each other in our own ways and that relationship isn't mutually beneficial. He actively seeks me out and does so of his own free will, he shows signs of distress at separation. I pay him for his services with food, medical attention and (most importantly) love.
