I must say, General, this is astonishing to hear! Do you realize that the men you treat as mere prey are valuable, unique human beings? They are what keep this world running; scientists, leaders, teachers and you kill them as if they were nothing!
Pathos
You've read my book, yes? You know all about my daredevil adventures to Madagascar, Egypt, India? I beg of you, Mr. Zaroff, from an excellent hunter to another, hunting men is not the way to cure your boredom. Around the world, there are thrilling beasts to slay and plenty reason to no longer kill your kind. Take it from me, please.
Ethos
If all this still doesn't convince you, think of it this way: one day you will meet your match and he'll surely alert the authorities of the atrocities that occur here when he wins the game and you let him leave. You'll be charged with murder, incarcerated, and likely never hunt again!