I look at it this way, and forgive me I cant help it.
Dogs trust in YOU. The owner to do what is best for them. And under no circumstance is putting the dog in a pit to fight is what is best for them. And dog. Any breed.
A dog cannot premeditate the idea that if he goes into a pit to fight he can get ripped apart. Maybe he can recognize the memory after he is put into the pit, but does not lie around thinking "hmmm, if I go into a ring and fight, I just may have my snout ripped off.." That is where the owner comes in. The owner premeditates the idea and then follows thru by entertaining the idea.
Weirdly enough, I find myself agreeing with you on this issue.
However, where do you draw the line? Is allowing a 40-55 lb dog to hunt and catch 85-500 lb hogs "in its best interest"?
Every day dog owners make choices for their dogs, and even if you took all the dog owners who were considered "good/great" owners, many of those would disagree with one another over what is in the dog's best interest. Heck, just look at the numerous dog food threads or the crating threads or the chaining/tethering threads. And that's just minor stuff.
Given a choice, if the dog could understand actually questions with every word, if you asked "Would you like to fight today? Are you sure, you may end up torn apart or even die" I find it hard to believe the dog would say "ok!" Bring on the pain!