Everyone involved with politics understands the current dynamic. It’s not hard to grasp. You take very tough economic times, add them to a heavy dose of political opportunism, and multiply both by the aggravating factor of a nihilistic commercial media, and what you get is ethnic scapegoating on a massive scale.Divide and rule has always been in the arsenal of illegitimate rulers. The author touched on a couple of them--Nazis and the Rwanda ruling class. But the Empire has made recent and extensive use of this technique in Yugoslavia, Iraq (also see this), and now in Afghanistan. (Read Strange Liberators by Gregory Elich)
With the rapidly disintegration of the US economy which is having serious adverse impacts on even the middle class, it is not surprising that the ruling elite is up to a lot of dirty tricks to keep Americans divided and at each others throats. Hence the mass media play on the Muslim mosque issue in New York and the anti-migrant worker issue in Arizona and the Southwest.
We can similarly expect to see efforts to divide Black Americans from Latinos, older Americans versus the younger generation. Fox media empire and all the other right wing organizations in the US are busy stoking the fires of intolerance and hate.