If one were to base their diet around moral responsibility, would eating only what the blade can cut be reasonable? Can it cut vegetables? Can animals be evil? Would training a cow to be evil in order to avoid starvation be morally justifiable?
Okay but if this became common enough that every paladin had a sword that only killed evil things and they also had the restriction that they had to only eat what they killed then it would be a good thing to raise evil creatures as food sources for the paladins, even though the people doing the raising are doing an evil thing.