Genocide is always fine for those who perpetrate them.
That solves the whole problem , if relativism is true. Otherwise, it is an uninteresting psychological observation.
To me, the interesting observation is : “How did we get here if genocide looks that fine?”
And my answer is: “Because for most of us and most of the time, we expected more profit while making friends than making enemies, which is nevertheless a selfish behavior.”
Making friends is simply being part of the same group, and making enemies is being part of two different groups. No need for killings for two such groups to be enemies though, just to express a different viewpoint on the same observation.
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I don’t agree with any killing, but most of us do otherwise it would stop.
Or co-ordination problems exist.
Of course that they exist. Democracy is incidentally better at that kind of coordination than dictatorship, but it has not succeeded yet to stop killings, and again, I think it is because most of us still think that killings are unavoidable. Without that thinking, people would vote for politicians that think the same, and they would progressively cut the funds for defense instead of increasing them. If all the countries would do that, there would be no more armies after a while, and no more guns either. There would nevertheless still be countries, because without groups, thus without selfishness, I don’t think that we could make any progress. The idea that selfishness is bad comes from religions, but it is contradictory: praying god for help is evidently selfish. Recognizing that point might have prevented them to kill miscreants, so it might also actually prevent groups from killing other groups. When you know that whatever you do is for yourself while still feeling altruistic all the time, you think twice before harming people.
We solve inter-individual problems with laws, so we might be able to solve inter-tribal problems the same way providing that tribes accept to be governed by a superior level of government. Do you think your tribe would accept to be governed this way? How come we can accept that as individuals and not as a nation? How come some nations still have a veto at the UN?