Drugs make people victims, not the enemy. Machines perform repetitive tasks and have no use beyond that. All wolf machines do is kill things, and not to just eat their prey. Wolves repetitively kill until there is nothing left alive for them to kill. Machines are designed to be efficient, so the metaphor also implies the wolves not only kill and kill, but do so efficiently.
Machines have no wills of their own, no feelings, and have no moral status.
We dispose of machines when they have no further use to us. Because we did not create the machine wolf, and because all it does is kill and kill, then we don't have ethical qualms about eliminating it. The llama owner, on other hand, saw the series of events as natural. Some metaphors distort rather than clarify- Not all metaphors are equally valid. We say that electricity flows in a current.