https://www.merriam-webster.com/dictionary/evil
We wrote these things down so that we describe them to each other. The concepts already existed. We didn't invent evil, we defined it but it was already there. We've also used arguments like this to separate ourselves from what consider be lesser, to distance us from our actions. This is mental gymnastics though.
Whatever you have to do to feel ok about eating a chicken is fine but pretending we have some better sense of self than anything else feels like hubris. If our position in the world is truly better because we can articulate out feelings and we're smarter, why don't we eat dogs and mutes and the mentally handicapped?
> why don't we eat dogs and mutes and the mentally handicapped?
This is exactly the kind of point you would have to bite the bullet on if you were to be logically consistent and made arguments for meat eating being ok because you believe animals are intellectually/morally inferior. If you believe a cow is ok to eat because they are not as smart then you would have to be ok (being logically consistent) with eating anything that is not as smart as you such as the mentally handicapped.
I think looking at how things in the animal kingdom work and using that as a justification for our actions is a very low bar. We have the cognitive and emotional ability to understand that things like murder/rape/etc. are wrong do we not? If you just take a small step from that and recognize the sentience of animals, it doesn't seem too unreasonable to afford them the same respect.
PS: I think the idea of good/evil is pretty reductionist to begin with, but I understand it's a common way of looking at things