This is probably true.Second, the reasons for low crime rates in such places as Japan is ...societal unity and cohesion. The society has a single unifying culture and long histories of traditional values, etc. I.e., they all think much alike on most, if not all, issues.
I suppose it's possible multicultural societies are inherently less stable and perhaps more violent. They may also be more creative. If the the trade off is to the positive then maybe it's worth it?
I still think that an educational system that shares some of the archeological findings fundamental to the development of of the various religions would be good for kids.