That can be also be twisted in other ways though:
In America too much White people is bad.
In China too much Asian people is bad.
In Africa too much Black people is bad.
The only countries that seem to be firm exponents of multiculturalism and ethnic heterogeneity are Western nations. Excusing those with work permits and temporary visas, you're not going to see China opening her borders to receive a crushing wave of non-Han Chinese people anytime soon, for example.
Nigeria is a pristine exemplar of how too much diversity can be detrimental to a nation's health: 8 major spoken language, 250 keystone ethnic groups, and two religions whose practitioners care absolutely nothing for one another. Throw a subtle pinch of African clannishness into the pot and you get a nice helping of
ethnic friction. I'm sure the Igbo are still a bit miffed over the atrocities committed against them during the
Biafran War.
Especially the human condition that believes things like needing to separate the races, or that having multiple races live together is a bad thing.
Having multiple races and ethnic groups living together isn't a bad thing in principle, but it runs sloppily when put into mechanical practice.
For example, most white neighborhoods will remain affluent, viable places for whites to live in until enough of the street becomes non-white. When this occurs, whites file out wholesale, taking their fluffy wealth and median incomes with them.
Once your tax foundation dematerializes, so does the neighborhood. White flight has been the undisputed champion at slaying communities across the country for the last 60 or so years.
But when white flight is put into a biological context, it becomes glaringly discernible that whites simply cannot help but do what they do. Evolution meticulously programmed them--bit by bit--to seek refuge with other whites, network with other whites, fight alongside other whites, reproduce with other whites, and otherwise associate with other whites.
I don't believe in racial separation, but I do see the freedom of association as a fundamental right that all people, irregardless of their color and creed, are unquestionably entitled to.
And in most of the incidents today, like Ferguson could be prevented with measures like improving the economy.
Ferguson's economy could be energized by bolstering it with black human capital, but one of the lesser known ramifications of the 1964 Civil Rights Act (besides the wholesome disintegration of black culture, the erosion of black social values, and the complete obliteration of black self-determinism) was that it kicked off a crushing, monumental episode of "brain drain" within the Afro-American community. Your elite and upper-class blacks, now interested in seeking fortune and prestige within richer white markets, formed comparatively safe and financially endowed ethnic enclaves across the country, in turn leaving the less fortunate, less capable, and more socially dysfunctional of their kin and kith behind in the ghettos.
Knowing them, they're not interested in making a return trip to their roots.
I know I wouldn't.