I had to think a bit before posting in this thread as it just makes me really angry. Senseless animal cruelty. Even is there is no other entertainment something should stop you when you hear the dog cry in agony. There is no "wheeee! Higher!!!", there is just pain and agony. Looking at the dog it is a recurring event.

Had the guy swung the dog into a rock to kill and eat it, I might not have liked the method but could somehow understand it so comparing it to animals being slaughtered doesn't cut it for me. We are cruel to chickens but it does not compare to the clip OP posted.
The Bulgarian tradition just traumatizes the dogs and causes no physical damage, unlike the tail method, but it is still sick. The tail method will cause for the dog to lose it's tail by amputation...
Somehow I can understand the guy swinging the dog, it's called peer pressure. On the other end I somehow wish a slow and painful end to the guy himself and everyone cheering for him. Strange perhaps, as I'm not normally like that. I genuinely believe in freedom in its broadest sense, the limit is reached when you hurt others. The dog swung in the clip posted by OP will need an operation to save it's live, will be in pain for days after every incident. Sick!