The detail that best reveals that Mr. Rainsford opposes Zaroff's idea of the ideal prey is Mr. Rainsford's response near the end of the passage when he states that he is a hunter, not a murderer. This statement shows the reader that Mr. Rainsford believes that Zaroff hunting humans as prey makes him a murderer.
He climbed out of the trench and made his way carefully back to the clumped bushes where the kitchen was.
In my opinion, there are two possible reasons.
First, the government probably does not think these guys are any kind of a threat to them. I mean, so what if there are some people out walking around when no one knows they're there? It's like the thing about the tree falling in the forest with no one around.
Of great value; not to be wasted or treated carelessly.
