What is 'evil', and does it exist objectively? The metaphysics of good and evil.
I clearer now in understanding why you brought up a previous thread. In comparing human beings with animals, it is definitely true that the big difference is that we have metaphysical and moral notions about good and evil. They live on the basis of instincts whereas we have language and the use of reason to guide us, so ideas of good and evil arise in that sense.
In your discussion of the golden rule, you bring in Nietzsche and his ideas are relevant. The reason why I have not discussed these is because there was a thread going on his criticism of moral views on compassion during the last couple of weeks. I think that it has only gone off the front page in the last couple of days, and you may be interested in looking at that thread.
Thinking about Nietzsche's ideas in the context of this specific thread though, Nietzsche's critique of Christian ideas does address the golden rule directly. In 'Beyond Good and Evil,' he states,
'the sentiment of surrender, of sacrifice for one's neighbour, and all self-renunciation morality must be called to account and brought to judgement.' He is opposed to asceticism but he is directly against social ethical concerns, favouring the 'will to power'. As far as I understand, he was not in favour of Nazism, but it is possible to see how his ideas could be used to justify such ideologies. I think it is questionable whether human beings can really go 'beyond good and evil' and to ask what that would truly mean? I often read Nietzsche's ideas as poetic truths, and in the context of pointing to some basic problems in culture arising from some aspects of Christianity, but I think how far one interprets Nietzsche is of critical importance. I certainly believe that if stretched too far, or too literally, his ideas could be used to make anything permissible, including oppressive ideologies and actual oppression in the world.