To explain its humor is to identify one of the most intriguing ethical dilemmas at the heart of any “deliberately adversarial” institution.
And yes, hunting is an adversarial institution of sorts; though it’s atypical in that usually one side in the competition (the hunter) is only ever on offense and the other is only ever on defense (the hunted).
The ethical dilemma at the heart of adversarial institutional design is also at the heart of this cartoon: is it ever morally permissible (or even obligatory) to do something within a legitimate adversarial institution that it would be unethical if done outside it? (Of course, some may question whether recreational hunting is in fact legitimate, but that’s another issue.) It’s never ethical to shoot your drinking buddy just for fun. Does it suddenly become OK just because one of you has now decided he is a hunter and you are prey?
And to suck every last bit of humor out of this cartoon — does harming your buddy (say, by driving him into bankruptcy) suddenly become permissible if it is “just business”? Is “just business” just business?
Well, yeah; maybe.