"It is generally undesirable for members of my own culture / social class to murder each other without just cause."
Before you respond, note that "Person X committed murder in Society Y and it was okay," is not a counterexample. You will need to present an entire culture which was
... and, I guess if you're still going for it, one which existed in Europe since 1000BC.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.