Basically this (totalitarian agriculture genociding alternative cultures) has happened everywhere and his thesis is that the total extermination aspect in particular is a novel aspect of farming culture, which did not exist for hunter-gatherers or herders. Not that violence didn’t exist, but exterminating violence was very rare.
He also connects it to the founding myths of Adam and Eve (who are cursed to practice agriculture, instead of being hunter-gatherers, and who believe they have the power of good and evil to know what plants and animals should live and which should die), and Cain (who sacrifices wheat, representing agriculture and land ownership) and Abel (who sacrifices a goat, representing a herding lifestyle).
If that sounds at all interesting to you should totally read it, it’s a really clever book!