Just because some raw feeding site claims dogs are carnivores doesn't make it true. Dentition isn't really a great way of classifying something as carnivore or omnivore. Herbivore or carnivore, sure, but it's much less obvious when trying to determine if something eats only meat or if they eat both meat and plant matter. Take a look at a Gray Fox skull, for example. They are an omnivore, and during some parts of the year their diet can consist almost exclusively of plant matter.
http://img2.etsystatic.com/il_fullxfull.261067294.jpgLooking at how a wolf eats is also very poor reasoning for how to feed a domestic dog. They aren't wolves, aren't really related to wolves any more closely than a variety of other wild canids, and haven't been wolves for a very long time. That is, if they ever even were wolves. There are 26 different DNA sequences between dogs and wolves, which is actually quite significant, and the exact wolf (if it was a wolf) has yet to be determined. It is entirely possible that the dog has always been a dog; that the original "dog" that was domesticated is simply extinct.
The original site of domestication has been suggested for re-evaluation with new findings in Africa:
http://www.genomeweb.com/african-dog-ge ... ion-neededInterestingly, unlike other domestic animals, when dogs have been breeding feral for generations their appearance does not revert back to its proposed ancestor (the wolf). Instead they take on a look not overly dissimilar to the Canaan Dog.
Dogs can digest plant matter, selectively eat it, and are capable of living off a plant-only diet. They are omnivores, of the opportunistic feeder style (AKA scavenger). Feral dogs don't form packs and hunt down caribou, they scavenge whatever they can off human areas like they've done for the past X amount of years. When they eat meat, it's either small things they manage to catch or rancid/by-product meat found in garbage bins.
For domestic dogs years ago, the diet would have been similar. Meat is a precious item, and wouldn't have been wasted on the dogs. For American breeds, the diet would have likely been very high in corn bread and (when they got meat) things they caught on their own or useless trimmings/rancid meats. If they were not omnivores from the beginning, we created them as one by selecting for dogs that worked the hardest on those kinds of diets.
Can they survive as carnivores? Yes. Can they survive as herbivores? Yes. Being a scavenger, the dog's digestive system is adaptable to a very wide variety of diets. Doesn't mean those diets are optimal or provide the best results, but it can be done and there are people who choose to feed their dogs that way. It's their dog, so it's their choice.