No, no, he was talking about Japan, right? Or, no, wait -- Switzerland?
Well, let's see what Google ("World's most peaceful countries") gives us.
Iceland tops that list, followed by Denmark, Austria, New Zealand, Switzerland, Finland, Canada, Japan, Belgium and Norway.
[Scanning list for diversity] ... Well ... let's see ... Those are some startlingly homogeneous cultures. I guess New Zealand is a bit diverse? No, not really -- 69 percent are "New Zealand European." OK. Canada? Well, according to Wikipedia, their largest non-European ethnicity is Chinese at ... 4.31 percent.
Bottom line: Evidence that more homogeneity means more strife = ... zero.
lllll AJ