Hey man. Great to see you on here.
I definitely agree that homogeneity often helps to minimize conflict. The caveat I would put on that, though, is that (as I am sure we both agree) forced inclusion and forced exclusion (via statism/borders/state violence) are illegitimate.
I think that there could definitely be (and that there already are) very multicultural societies that are able to exist in relative peace, but that when the state forces people to "intergrate" or to stay away, based on non-private property-based "laws," everybody loses.
Individualists know that if principles are shared, private property is respected, and association is neither forced nor prohibited, there can be peaceful societies of all types--homogenous or otherwise.
It is largely the statist potato types that are not able to handle individuals not of their own cultural background, but again, there is absolutely nothing or illegitimate or wrong about preferring to associate with one's own culture, either, even exclusively. The problem is when the state ignores private property and attempts to force this, or prohibit it.
It's a tough issue. But pretty simply solved if everything is privatized. One example that stands out to me, though, is the south side of Chicago. In many ways quite homogenous, and still one of the most dangerous places in the world, regarding homicides.
Hope we can talk about this more soon.
You too!