Multiculturalism and megagovernment

A friend of mine is interested in whether any nation can endure when there are many different, competing cultures within it. History provides a consistent answer to that question, neatly summarized by this quote from a fellow blogger:

In a multicultural society lacking cultural cohesiveness, such as the USSR or Iraq, there must be an authoritarian central government to force the differing groups together. That's why free, representative government only arises in culturally unified societies. As the US is steered toward multiculturalism, the government must of necessity become more authoritarian because the central government cannot emulate (L.A. Mayor) Villaraigosa and make everyone happy -- it has to take sides at some point.

That's why court dockets are increasingly filled with cases like this one. In a nation increasingly lacking any common frames of reference, someone has to decide what view(s) are permissible in the public square, and which are odious to society. Those in position to make such decisions wield vast, nearly unaccountable power to shape society in the direction they choose.