We have a built in illusion that morality is discovered, not invented. But our moral flexibility over time is huge, and can encompass things like slavery and genocide. It could as easily encompass farming and eating live babies, or other horrors up to and including human extinction.

To the extent that fiction acknowledges and explores such moral spaces it's natural for it to be contentious. Exploring alternative moralities is necessarily immoral to the prevailing morality. A culture of profound tolerance is required for such explorations, and such cultures are evanescent and poorly distributed.