We had a similar issue here about a year ago... A deer was hit by a car and flopping around on the road... A passer-by got out of his car and attempted to end its suffering with the only tool he had, that was legal (it was within city limits so no firearms allowed), which happened to be a shovel!!!!
A nice older lady was appalled by the sight of a "rough looking young man" beating the deer with a shovel and phoned the police.....
The man was charged with animal cruelty for trying to quickly end the suffering of the deer. I forget if it was bear season and the guy had a rifle or if he was very close to his house but he went out of his way to not shoot the animal because here in Canada it is not legal to fire a gun bow or airgun in city limits... This guy was following all relevant laws and trying to stop an animal's suffering... He was still charged and had to stand trial... He escaped jail time but had to pay a fine and attend counseling for a set period of time.
I don't agree with what Vick did but they were his dogs... a breed of dog that would not exist if not for fighting so he can do as he pleases with what he rightfully owns as long as he isn't randomly grabbing other peoples dogs to fight and as long as all participants and spectators to the fights are there without being coersed who cares!!!!!!
How many people's Cougar, Bear, Wolf, Hog, Coyote dogs get killed every year "fighting" wildlife. They're bred for it and they love it... Same with Pit-bulls. I currently have a wolf/husky cross from a sled kennel who lives to fight. Check out how often sled dogs will fight to the death, and how many polar/antarctic expeditions were almost scrubbed because of fatal dog fights. I don't make her do it.. in fact I can't stop her from doing it!!!!!!!! She has killed two dogs that have wandered into my yard. Dogs that were chasing our horses to death before she was let into the field to stop them. She grabs the other dog by the throat (wolf blood not training) and rag dolls em, death is very quick. She has done this from puppyhood. She has also saved our other dogs from coyotes on four separate occasions.
The long and the short is that fighting other animals (hunting) or fighting other dogs (pit fighting) or herding other animals are all just modifications of the prey drive and part of ordinary wolf (dog) behaviour. People are people animals are animals, we are only distantly "Family".