Rainsford says that he is a hunter and not a murderer because he is refusing to participate in the game as a hunter, and does not yet realize that he is playing as the prey.
Sanger Rainsford is a world-renowned hunter who gets the surprise of his life when he falls off his yacht and swims to Ship-Trap Island. He has been warned that the island has a spooky reputation, but he had no idea how far from home the rumors hit. The island is dangerous all right, and not for the reasons the sailors thought. A homicidal hunter has turned the island into his own personal playground, and he does not distinguish men from animals.
When Rainsford first lands on the island, he immediately notices a small caliber bullet appears to have been used to hunt what seems to him to be large prey. This surprises him. He does not understand how a hunter could be shooting large animals with a small gun. It is a sign of things to come, though, foreshadowing the kind of hunting that is really going on there.
Coming to a huge chateau, Rainsford is again surprised. What would such an elegant house be doing in the middle of a Caribbean island? He announces himself to the man who answers the door as not a threat, but the man is huge, and does not talk. It is the second sign that something is wrong, if he is paying attention. He has just met General Zaroff’s assistant, Ivan.
General Zaroff introduces himself, and it is clear he already knows who Rainsford is.
In a cultivated voice marked by a slight accent that gave it added precision and deliberateness, he said, "It is a very great pleasure and honor to welcome Mr. Sanger Rainsford, the celebrated hunter, to my home."
Rainsford has written many books on hunting. This is how Zaroff knows him, and why he is interested in him. Here he has, not just an ordinary man, but an expert at tracking prey and evading it. Rainsford is indeed the most dangerous game. Zaroff lets Rainsford in on the secret over dinner. He is such an expert hunter that he became bored of hunting every kind of animal, and decided that people were much more interesting. Rainsford is shocked by this revelation.
"I can't believe you are serious, General Zaroff. This is a grisly joke."
"Why should I not be serious? I am speaking of hunting."
"Hunting? Great Guns, General Zaroff, what you speak of is murder."
Zaroff goes on to explain why he feels that he is doing nothing wrong, and it is Rainsford’s worldview that is incorrect. Rainsford is old-fashioned and short-sighted. After all, the world is made of the weak and the strong, and only the strong should survive, according to Zaroff’s philosophy. It is not a dissimilar thing to what Rainsford said earlier, when he suggested that the world is made of hunters and those who are hunted. He had no sympathy for the prey when it was a jaguar, but humans he refuses to hunt.
Of course, Zaroff does not really give him a choice. He makes his opinions on the subject quite clear, and the general gets what he wanted all along—a real sport, with himself chasing the world’s second greatest hunter.
Tonight," said the general, "we will hunt--you and I."
Rainsford shook his head. "No, general," he said. "I will not hunt."
The general shrugged his shoulders and delicately ate a hothouse grape. "As you wish, my friend," he said. "The choice rests entirely with you. But may I not venture to suggest that you will find my idea of sport more diverting than Ivan's?"
He explained earlier that anyone who does not agree to the game will be beaten to death by Ivan with a whip. Rainsford is shocked by the fact that he is being forced to play the game as prey. He thought he was going to be asked to be the hunter.
The game tests Rainsford’s skill, and his emotional endurance. However, he may also bend his moral principles. As sure as he was that he would never resort to murder, he does end up killing Zaroff (and Ivan). Killing was never part of the game for the person playing as prey. Was Rainsford protecting the future participants, or getting revenge? We know that he feels no remorse for his actions, but you will have to interpret that for yourself.