I thought this was going to be a thread about "which foods is it best to feed your dwarfs on, and which foods should be avoided." Personally I like to order in food from Giant creatures (especially GCS and Giant Toads) on the grounds that a) the more expensive the food, the happier it probably makes the dwarf and b) I like the idea that my dwarfs are commissioning the death of GCS.
I suspect a *gutter cruor biscuit* should probably be avoided, too.
IRL I'm a veggie, although more from a distrust of meat processing than from a desire not to slaughter hapless animals. I don't think it's possible to live without causing harm to some creatures somewhere, but I also don't believe in wasting time agonising over guilt for something trivial like theoretically denying the right of a bunny rabbit to graze in the garden
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As for DF, I personally try to cause the poor dwarfs the minimum harm practical (although as the Terminator once remarked after seeing a couple of dwarfs running around: "It is in their nature to destroy one another"); I have no qualms about exterminating goblins and wildlife, but I won't (usually) kill dwarfs for kicks, and I won't murder traders either.
I'd quite like to see the "thoughts" of dead dwarfs updated when they die, so that instead of reading "he has sustained major injuries recently" it might read something like "was killed by suchandsuch and is communing with insertworshippedeityhere in heaven" or "is in hell awaiting the arrival of stilllivingdemonworshippedbythedwarf" and things like that. It would give more "closure" to the death than having them just listed as if they were still alive.