What does the phrase “sporting proposition” most closely mean as it is used in paragraph 95?

The general laughed with entire good nature. He regarded Rainsford quizzically. “I refuse to believe that so modern and civilized a young man as you seem to be harbors romantic ideas about the value of human life. Surely your experiences in the war — ”

“Did not make me condone28 cold-blooded murder,” finished Rainsford stiffly.

Laughter shook the general. “How extraordinarily droll29 you are!” he said. “One does not expect nowadays to find a young man of the educated class, even in America, with such a naïve, and, if I may say so, mid-Victorian point of view. It’s like finding a snuffbox in a limousine. Ah, well, doubtless you had Puritan ancestors. So many Americans appear to have had. I’ll wager you’ll forget your notions when you go hunting with me. You’ve a genuine new thrill in store for you, Mr. Rainsford.”

“Thank you, I’m a hunter, not a murderer.”

“Dear me,” said the general, quite unruffled, “again that unpleasant word. But I think I can show you that your scruples30 are quite ill founded.”