Respectfully I want to creep up towards a presumptuous argument and say that you won't argue for euthanizing pugs because your gut tells you that whatever trouble pugs have due to their (many) health problems, a well-cared-for pug is generally a happy dog, and is not in fact living a life of overwhelming suffering.

We own a rescue mutt and a brachy purebred, and while I can't get inside the heads of either of my dogs, I would have absolutely no trouble telling you which of the two dogs is enjoying its life more. :)