Hello. I’m the “activist” in question here. I’m also someone who spent ~8 years interrogating physicians on medical science early in her career, but that’s neither here nor there…
I should mention, I did send OP links to a sampling of canine cognition research which is illuminating on the subject of the human-dog bond. Curiously, and for reasons only he can explain, OP appears to have dismissed that data out of hand. (perhaps not all that surprising, given that he chose this forum as his go-to source for information as opposed to, say, a simple Pubmed search?)
Having assumed I fulfilled my duty with that proffer, I was to loathe to bother in this forum. That is, until I skimmed through some of the comments posted thus far and was taken aback by the paucity of helpful and/or credible information. Alas, I’ll keep it brief.
The modern dog is a creature that is specially adapted to live alongside of us, hence the “human-dog bond”. This is after all, a species that came into existence by ingratiating itself to humans some 30,000 years ago. Over the millennia that followed, we then selected for favored traits to create the best hunting, herding and guarding companions (our methods were crude at best throughout this period; specific dog breeds are only a very recent phenomenon, actually).
The result is an animal today that is specially attuned to interpret our facial expressions, our emotions (dogs are the only animal, outside of humans, shown to have this ability; primates have the capacity among other primates but not across species), our voices, our speech, our gestures (better than chimps, in fact), and even our intent to some degree. Dogs show preference for their owners over other dogs and even food in some studies, and they instinctively run toward humans when anxious or fearful, whereas cats and horses are inclined to run away under stressful conditions. When dogs stare into our eyes, it releases the same hormone in our brain -- and theirs -- that bonds mothers to infants (by contrast, wolves will interpret a human stare as aggressive and avoid eye contact). It’s all there in the scientific literature, and more.
But hey, why give any stock to the words of a mere “activist” on an anonymous forum. Instead, I urge you to consider what some of the experts themselves have to say about the unique relationship (then visit Pubmed):
Dr. Brian Hare, author of The Genius of Dogs and founder of the Duke Canine Cognition Center:
“Dogs show an affiliation toward humans that is unlike any other in the animal kingdom. They prefer humans to their own species and can behave like human infants toward their parents.”
Dr. Gregory Berns, author of How Dogs Love Us and head of The Dog Project at Emory University:
“It’s not the case that they see us as ‘part of their pack as dogs,’ they know that we’re something different— there’s a special place in the brain just for us. What we’re finding with the imaging work is that dogs love their humans—and not just for food. They love the company of humans simply for its own sake.”
“All the things that we’ve done with the brain imaging—where we present certain things to the dogs and map their reward responses—we see analogous brain responses in humans. Seeing a person that’s a friend or someone you like, these feelings are exactly analogous to what a dog experiences.”
“Our findings show that dogs have an innate way to process faces in their brains, a quality that has previously only been well-documented in humans and other primates.”
Dr. Attila Andics, neuroscientist at Eötvös Loránd University in Hungary: “Dogs process both what we say and how we say it in a way which is amazingly similar to how human brains do.”
Dr. Luis Concha, National Autonomous University of Mexico's Institute of Neurobiology: “Our study provides evidence that human faces are truly special for dogs, as it involves particular brain activity. To dogs, the human face is no ordinary thing.”
Dr. József Topál, Hungarian Academy of Sciences: “Our findings reveal that dogs are receptive to human communication in a manner that was previously attributed only to human infants.”
Dr. Ludwig Huber, University of Veterinary Medicine Vienna's Messerli Research Institute: “Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before.”
…I think I’ve made my point.