The law of nature is not an actually law. Following natural instincts is not an ethical way to live your life. You don’t rape somebody when you want sex or steal candy from a child when you are hungry. You should not kill an animal when you want to barbecue their flesh.
I could argue that ethics and morality are illusionary, and that no other animals exhibit the need to accuse another animal of murder, rape, or stealing. And they still enjoy their lives, feel hunger and pain, pleasure, etc and so forth.
If you could do away with ethics and morality completely to where we were not even aware of "good" and "evil" as concepts .... we could still live our lives and enjoy sex, food, play, empathy, fear, pain, etc and so forth. I don't see how rape, murder, stealing would come into the picture because we would not have the capacity to be aware of those concepts. We would just do them and move on and get over it, continuing to live our lives. Possibly.
Ethics and morality are "necessary" evils because people think they
deserve to have "good" things happen to them and not bad things, and people should be held accountable for their actions. Reality, is that the universe doesn't care about what we deserve or justice being issued. I don't see other animals doing it either. Just us. I view it as a detriment, not a evolutionary benefit.
Now, don't forget that barbecued meat is an aroma pleasing to the Lord ... the Most High is a glutton for mutton.