Sri Lanka started coming apart within a decade of receiving its independence as a free, democratic nation in 1948. The Tamil minority was not as dominant in its economy as the Chinese minority in Malaysia and other Southeast Asian countries, but still Tamils were over-represented at the top in business, in the professions, and in education. That was enough to allow the Sinhalese majority to be mobilized politically against them by ambitious politicians.
Even though there had never been a single race riot between the Sinhalese majority and the Tamil minority during the first half of the 20th century, there were many in the second half, punctuated by unspeakable atrocities. Eventually Sri Lanka descended into outright civil war, in which this small island nation has suffered more deaths than the United States suffered during the Vietnam War.
Similarly, according to Professor Chua, an authority on ethnic conflicts around the world, there were no major outbreaks of violence between the Hutu and Tutsi in Rwanda in the first half of the 20th century. Then majority rule brought ethnic polarization and horrifying massacres.
What about counter-examples of free, democratic, free-market, non-Western societies where an ethnic minority is blatantly more successful in the economy than the majority population, but where the people live at peace with one another? You supply those examples. I can't think of any.
Professor Chua's thesis is especially important in an era when American foreign policy sometimes seems to be pressing our allies and others to become democracies with free markets -- whether or not each country's social conditions or cultural traditions provide the prerequisites for letting that particular combination be a blessing rather than a curse.