They belonged to a group called "them" - this made them different from "us" and we could decide that we didn't, indeed couldn't, understand them, and that they didn't have feelings anyway because of course they were "them". Therefore it was all fair.

Have you noticed the way that those who espouse racism also shut out people with disabilities. Same principle. And terrible in this day and age.

It's a great article and gives some hope for humanity.