Well, first of all I don't have the thick skin and heavy coat of a hunting dog. I'm also a lot taller, so blows from a man are going to land directly and with a lot more force. A typical Springer is about 19-20" tall. My dog is 20 1/4" at the shoulder, and I'm not very tall, but I still have to lean way over to pet her or grab her collar (unless of course like most Labs she's standing on her hind legs and grinning at me). Add that to the fact that this guy was drunk, and a lot of the "whaling" the witnesses saw was blows that didn't land and windups that went nowhere. That would explain the relative lack of injury. As to why he didn't petition for the dog back, it was a recently acquired rescue and he decided it wasn't worth the trouble.
I could see a wide range of punishment for this guy, including an order that he undergo "obedience training" at his own expense or an order that he not own any animal for a period of years. But a felony conviction is way, way too much. You may not get a felony conviction for assaulting a HUMAN BEING, for heavens sake. (Simple assault or battery are still misdemeanors in a lot of states.)
I think I might see a pattern here. People with large to medium size dogs seem much more forgiving of the guy than cat owners or people with no pets.
I have a Golden and an Australian. Both are great dogs and while they don't compete both know the basic commands and go everywhere with me. I haven't so much as raised my voice to them in years. We have been together long enough that they know what I want them to do before I do.
When they were young though. Well lets just say that 6 mo. old puppy/dogs often need an attention getter. I carried a rolled up newspaper in my back pocket at all times.
I was lucky in that my dogs were both fairly quick studies so that period didn't last long, but every dog owner goes through that difficult training period before you can relax and know that your dog won't immediately run out into traffic if let off leash.