The following is what I think I remember reading, but I stand to be corrected by anyone who is an expert:
The general rule in nature is tha carnivores eat herbivores, not other carnivores. The flesh of carnivors is toxic, and, over time, harmful,causing various unpleasant neurological diseases, which are significantly commoner in Korea than elsewhere, because of their habit of eating dogs. As they say in Korea: "a dog isn't just for Christmas: if it's a big one, there'll be plenty left over for boxing day". [Edit] - however, I can't find anything about this on google, so it may be cobblers. There are variousclaimed health risks fro dog meat, such as rabies and various parasites, but none that are absolutely intrinsic to the nature of the meat.