Retorts involving a country's homogeneity and ethnic make-up as a reason social policies work well in that country usually carry a more sinister unspoken subtex

Retorts involving a country's homogeneity and ethnic make-up as a reason social policies work well in that country usually carry a more sinister unspoken subtext, i.e. that ethnic diversity makes an environment hostile to social policies, and/or that some populations are intrinsically unfit for social policies. I don't want to go too far down that lane, so let's say that guessing the reasoning underlying this argument and examples of populations that argument is typically applied to are left as an exercise for the reader.