I'm only halfway through the main campaign but 30 hours total.But mother earth and the belief system of the Nora people focuses heavily on Mothers. Mother Earth is huge for them and they almost name everything mother peak, mother square, mother blah, etc... So if someone doesn't have a mother I can see how they'd be against that considering how fanatical some of them are.
Its a really interesting concept, and it makes me connect with Aloy right from the start. I'm really impressed with the story so far.