This thought experiment can be compared with a real world one.

The (White?) Rhino is an endangered species due to armed horn poachers. Armed Game Wardens, financed by foreign governments and NGO’s, try to stop them, with, I believe, loss of life on both sides.

In this case the humans are willing participants. It doesn’t ‘feel’ wrong to me: either to submit to the risk of death as a warden, or to kill poachers.

Why do we feel repelled by murder in the Panda case, but, somehow, it is justified in the Rhino case?

Is it due to the relative moral weights of Pandas, Rhinos and humans? I don’t think so. The Utilitarian stance of the protagonist seems to be undermined, as it so often is, when we try to justify another human’s murder “For the Greater Good.”