Very interesting analysis, and I think I agree with all of it.

But I would add that some norms are more stable than others, and I don't think that "diversity" is an easy one to stabilize. It's partly paradoxical: diversity as a norm is not itself diverse, so as you admit more diverse cultural elements with their own non-diverse norrms, you actually undermine diversity. (Witness the tension between traditional enlightenment values and Islamic ones in, say, Turkey.)

Secondly, a norm isn't a norm if it doesn't draw any distinctions. But diversity is all about embracing distinctions! So what distinction can you draw--the difference between diversity and sameness?? Thus, people who strongly embrace diversity tend to antagonize the majority norms (e.g. in the United States, those who most promote diversity say, at times, that the U.S. "has no culture" and therefore any norms can be ignored, and/or that its culture is "whiteness" or "patriarchy" or somesuch and is evil and therefore should be disrupted as much as possible). If you believe strongly in the norm you're almost forced to take on the biggest battle possible because any smaller battle would be a battle to decrease diversity.

So, oddly, a norm that one would naively think should be especially low-strife to enact ("hey, let's chill, we have different ways of doing things, it's all good") have been turning out to be the exact opposite.