First of all, you've created a strawman out of what you assume I believe.

> But it strikes me as very human to define in-groups people like you and people or beings other than you and using that as justification to do horrible things to them.

This is a behavior nonspecific to humans...not sure if you've heard of it, but there's this fascinating emergent behavior among wild animals that naturalists have occasionally observed - in colloquial terms, they've labeled it "predator and prey".

Comparing the industrialized usage of animals like pigs and cows to "predator and prey" is not a good comparison in my opinion. For the record I'm totally fine with indigenous humans hunting and killing animals. The scale and industrialized nature is what makes a big difference I find, the same way killing someone in self defense and genocide both involve the murder of humans, yet there is a qualitative difference I wouldn't ignore.

Many predatory species engage in behavior that limits their hunting to avoid making their prey extinct. Right now extinction rates are >1000x above the baseline a couple hundred years ago. What we are doing to the biosphere we are currently part of is short sighted self sabotage - which is in large parts fueled by a wide spread human supremacist mindset.