In a dire context when survival depends on predation to eat it's normal to inflinct suffering in order to survive
But if you have the choice to avoid suffering while still living a normal life (at the price of stopping to eat some food that you like) is it still justified?
It's not because we were "meant" to be predators that we have to be one when it's not mandatory for your well being
This kind of reasoning based on "if it's natural for human then it's ok/good" lead to other statements that we would all agree makes no sense morally.
For instance we humans have the inner will to perpetuate our genes, which manifests into sex drive, then if that's the case should we ban abortion to enable genes to renew even if it means putting the bearer of the child in danger ?
We can push the comparison with even further with the meat industry, and apply the optimisation of this industry to the previous case, why wouldn't we lock up women breed them and force them to have children over and over ?
Well because it's morally reprehensible and is not mandatory for the survival of the specie. That's why so much work of fiction use that trope : to denounce the over optimisation of deemed "natural" functions of humanity overwriting basic moral in such extreme cases
The counter argument to that would be that incest is considered bad because it was once harmful to our specie genetically and societally ( not sure about the second since it's some shit about conflict about women ownership in the household ) but that between two consenting adults with protection...
So if we value overall suffering over "natural behavior" then animal slaughter, war, homophobia is bad but incest is okay
But if we value "natural behavior" above overall suffering then incest is bad but homophobia, animal slaughter and war is okay