My house, my rules; but I’d help you start yours.
Cultural relativism is the position that there is no universal standard to measure cultures by, and that all cultural values and beliefs must be understood relative to their cultural context, and not judged based on outside norms and values. (more)
Every social norm limits behaviors, and thus cuts within-culture evolution of those limited behaviors. But good norms can improve things enough to allow better evolution of other behaviors. So the world needs cultures to be able to create and sustain norms on whatever topics they want, of whatever strength they want.
But the world also needs enough varied cultures undergoing enough selection pressures to evolve good norms. And so new cultures need to appear frequently. Yet cultures vigorously enforcing their current norms seem an obstacle to making new cultures.
Thus I predict that cultural evolution should eventually select for some variation on the first line above of this post:
If you stay in our shared culture, you must abide by its norms. But if you are serious about starting a new “cult”, we’ll bend over backwards to help you, and give you space to try new norms.
No, one wouldn’t let each toddler declare themselves a new cult at bedtime, to stay up late that night, and then convert back in the morning. To qualify for the cult exception, you’ll need enough independent-enough people trying to be insular enough to give your new cult a shot. And you’ll have to stick with it for a while. But if you can show us you are serious about this, we will eagerly support you. Just like parents helping kids start new households. And we’ll also try to give you some space, but less, when trying to plan and coordinate possible new cults.
Today we tend to classify cultures as tight or loose depending on how strongly they enforce their social norms, and how much they tolerate deviance. But cultures tend to extend these same attitudes toward both cultural insiders and outsiders, as well as to insiders trying to become outsiders. But what cultural evolution should most promote are cultures that are relatively tight re most members, but relatively loose re breakaway cults and cult-wannabes.
Maybe this is what deep multiculturalism should really mean. Not so much a generally accepting cultural relativism, but instead suspicion and even hostility to co-existing rival cultures, and moreso as they differ more, but indulgence of and aid to descendant cultures, even when they are expected to become very different. Just as with AI.
Added 31May: In this nice 2019 essay, Freemon Dyson reviews the history of our understanding of evolution, and emphasizes how biological evolution developed special features to encourage the creation of new species. I’m suggesting in this post that cultural evolution will also create new special features to encourage the creation of new cultures.
deep multiculturalism means looking at how diversity arises and is maintained despite the same processes throwing up intolerant one-ist options, one can look at Mary Douglas et al perceptions of risk as one relative structuralism to do this via individual/group choices, but this does not account for the urge to world in the first place (the OP displays this urge in the phrase "But the world also needs…" which is also a should as well as a need. see https://www.academia.edu/40978261/Why_we_should_an_introduction_by_memoir_into_the_implications_of_the_Egalitarian_Revolution_of_the_Paleolithic_or_Anyone_for_cake
"But the world" see ... revisiting the difference in my usage of 'moral urge', 'worldbuilding' and 'to world' https://whyweshould.loofs-samorzewski.com/worlding-on-saturday-morning.html crossposting https://whyweshould.substack.com/p/worlding-on-saturday-morning