Compare to bilingual education.
Which sounds really nice if you don't think about the details, but gets problematic when you start considering them. Again, even leaving aside the reality of widely differing moral/value judgments and sticking to things we can all be more-or-less be rational about like tipping parameters, some culture is going to have to "win" for this to work smoothly. So, you know, once you start thinking about it this way and start thinking about the concrete details of how people interact within cultures, it completely ceases to be surprising that cultures still physically/geographically self-segregate even within the beautiful tapestry of diversity... how could it be otherwise? It's very challenging to try to go out into the world and interact with the intersection of all possible cultural rules (that is, the things agreed upon by all cultures universally), because the intersection is really quite small when it comes to cultural protocols for trade and such. You could spend hours putting together lists of things that are mandatory in one culture, and verboten in another. For instance, this recently went by on HN: https://news.ycombinator.com/item?id=9684152 Even if both you and the other person know all the possible protocols, how do you negotiate which you're going to use, when for most people these are really ingrained assumptions below the conscious perception? (And would not this metaprotocol have to come from somewhere and be some form of imposition?)
And to be clear, I mostly mean this post as food for thought, rather than a clear and confident claim of a specific opinion. (Yes, I did express a preference in my previous message, but I'm trying to go more food-for-thought here.) I've also carefully phrased this in terms of "cultures" and not "ethnicities", as in the context I'm discussing, there's only a correlation between the two, not direct causation, and adding in "ethnicities" can just end up clouding our thinking. You get these issues when interacting between countries and stuff too, which is why it's food for thought in general and not a specific attack. It's one of those things where even a smart person can initially think it's a set of very easy problems to solve if you think about it only at a high level, but when you start getting into the details quickly explodes in complexity. Humans are irreducibly interesting!