Think it over. I'm still the only one here who can use a can opener.
The giant cat has the power to kill the man, who is attempting to defend himself. His best defense: he reminds the cat that he's the only one who can open canned cat food by using a can opener. It's funny because, even though the cat is big and powerful, the point the man brings up about the cat's reliance on him is still a valid reason for the cat to not kill him.