Michael Vick is innocent! At least when it comes to violating the nonaggression principle, he's still a piece of shit. A lot of people cry that this is the weak spot of libertarianism, that it does not leave room for animal rights, but I happen to feel that it is one of its many strengths, because animal rights are nonsensical and invalid. For starters most people who say they are for animal rights do not even follow their principles correctly, for if animals have individual property rights(the only rights an organism has naturally), then they would have the exact same rights as humans. They would be able to own property, sign contracts, and defend themselves with force. If an animal injured a human than that human would be able to take them to court. The only people that actually follow animal rights logically are radical organizations like PETA, and consequently everyone thinks their nuts.
The problem is is that animals do not meet the criteria for property rights that humans meet. They aren't self aware, and they cannot homestead their surroundings. Hans-Hermann Hoppes argumentation ethic says to argue against property rights through homestead is to affirm their truth because you cannot have an opinion without owning yourself. An animal cannot have an opinion like that. These sort of property rights based on homesteading are the only rational and moral way of social organizing, they lead to the least amount of conflict and most efficient use of resources, and all other ways of organization involve arbitrarily assigning everyones rights to some coercive organization, so we must conclude that this system of rights is sound, and sense it invalidates animal rights, we must conclude animal rights to not be sound.
So keeping all this in mind, from the perspective of what should be legal(Or to put it more directly, what activities is it OK to use force to stop) dog fighting, unless used with dogs stolen from others, is simply a destructive use of ones property, and should not be criminalized. That is only from a narrow libertarian legal perspective though, and most people do not understand that there is more to a libertarians moral compass than that. There is lots of different opinions an individual libertarian can have on a multitude of things they feel is right and wrong, and all they have to do to be a libertarian is recognize that they can't force people to follow all of these.
In a free society a Libertarian can enforce their ethics on something, by ostracizing those that engage in what they find bad, and fraternize with like minded individuals on the subject. For instance, I think proprietary software is unethical and the free software model is the only ethical way to release software. I recognize that it is not an initiation of force though to release proprietary software so I simply try and ostracize firms that engage in that practice.
When it comes to animals, while I do not at all believe in animal rights I am a firm believer in animal welfare. I feel it is wrong to cause unnecessary suffering to an animal even if its yours because even though they are not people with rights they clearly suffer when harm is done to them, and therefore someone who causes more harm then necessary to them is being cruel and despicable, and I would ostracize them. So while I feel Michael Vick did not commit a real crime he still should be ostracized by everyone in society for being cruel.
While were at it lets legalize cock magic too.