Perhaps I should say immediately post hoc rationalisation, or as-quick-as-thought rationalisation, those things that we justify in some way as soon as our desire becomes conscious.
I was listening to Patrick Wyman talk about the culture-historical method of archaeology and of understanding the past. He of course had to mention right out of the gate Nazis! to warn people away from going anywhere near that cliff or anywhere even in sight of that cliff. (Other cliffs, over which more people have fallen, remain unmentioned as usual.) So yeah, I get it. Don't be like them. I think I've heard that like - all my life. I digress. The association being offered was that this method of associating culture and ethnicity leads to evil thinking about what ourselves and others are like, and then to evil actions.
Digression continued: The focus should be on the fact that is an unreliable method of identifying culture from ethnicity or ethnicity from culture, with America being a great current example. People from widely different genetic backgrounds have similar language, material culture, and customs here. It is good to keep that in mind when looking at archaeological material, whether humans or objects. Don't assume they all used these objects - some may be prestige imports obtained for the rulers in trade - nor that they spoke the same language. People often speak two or more languages and use them in different circumstances. This was true then and now. On the other hand, it's place to start looking. If you uncover graves 200 miles west of a culture which has written records in language A, a distinctive type of pottery, and a ruling elite with R1a y-haplotype, and your newly discovered group also has R1a y-haplotype, something close to language A should be your tentative hypothesis. Now that we know that migration does occur more than was credited fifty years ago, theories related to the disfavored one are coming back. (Just don't be a Nazi, got it!? I hear they are just everywhere these days.)
So the idea is that this sort of thinking leads people to do bad actions. We tend to do this about all groups. There has been a great deal of discussion recently about why Russians act like they do, and before that it was why all those largely-Muslim people from the Middle-East act as they do, and why Americans expanded westward, and why Christians went to war against pagans, and then other Christians. It seems the only thing to talk about in attempting to understand the world.
But what if most of it, or (gulp) all of it is just later rationalisation? What if people just do things because they can? They have stuff and we want it. There are other people who aren't us through that gap so we had better subdue them for our safety. It's a bit frightening, because we would then have to look out on a world we don't have much control over. It's more comforting to believe we have better reasons, not only for our own consciences, but in hopes of getting other people to act in ways we like. Like either trading with us or going away or something.
It is not only the perceived overall aggressors doing this. The current narrative is that the Native Americans attacked Europeans because they felt attacked and invaded themselves and were just defending their land. Well, sometimes. Sometimes they attacked because the Europeans had good stuff and they wanted it. If that sounds insulting to the indigenous peoples, as if they are primitive, I'm also saying that's pretty much what the Europeans did as well. The New World had stuff. Let's go get it.
I think it is more likely that the bad attitude flows in the other direction. If we want to defend our territory from you, then you must be terrible in some way. If we want to enslave you... gee, maybe we really shouldn't do that - hey, I know! They must not have souls. Problem solved.
I don't believe the strong version of what I just put forward myself. I think what we believe about others can be modified by cultural factors, not just our primitive amoeba-seeking-food responses. I just think those cultural things look more and more like rationalisations, less and less like reasons, with every passing decade. I made a great deal during the first years of this blog about tribalism - not between Tutsis and Hutus or Flemish and Walloons, but among the various internal cultural tribes in America and the West. I made much reference to the Arts & Humanities Tribe I grew up in but felt was going in bad directions. I focused on ideas. Yet sometimes I read an analysis that cynically notices that particular legislation or cultural changes means more and better jobs (status, food, mates) for one tribe, so they like it. All the purported reasoning, charts and graphs, and historical examples are just tacked on for show. Down this tunnel there is more mash, and I have an instant justification why it should be ours.
It may be why they have to see so many Nazis now. It's a great reason to take someone's mash. The others can't be just any old type of competitor, they have to be crammed somehow into the category of Best Enemy.

