Can slavery ever be justified?

[Greta]

There is an explanation," don Juan replied, "which is the simplest explanation in the world. They took over because we are food for them, and they squeeze us mercilessly because we are their sustenance. Just as we rear chickens in chicken coops, gallineros, the predators rear us in human coops, humaneros. Therefore, their food is always available to them."

I've thought about this a lot. I do think we are farmed in a sense, but we ourselves are not the food product but the producers to be milked.