It is all about class. Think about the typical upper middle class professional (we will exclude the truly wealthy, who in fact run everything, but the UMC sets the cultural table and tilts the elections).

A typical UMC person deals with smart, nice people all day, is pulling down hundreds of thousands of dollars each year (and more, if he lives in an expensive urban center), his kids are going to good schools (either pocketed public schools in wealthy neighborhoods or private schools), crime is low where he lives and on and on. His sense making has always been provided by the received wisdom in those good schools growing up and by the usual media suspects: NYT, WAPO, the Atlantic, PBS, NBC, etc.

He goes from good job to good neighborhood and there is nary a discouraging word to break up that rosy picture of things. And if then the NYT tells you that something is amiss, you instinctively believe them since they have been your faithful media companion all along life's journey. And it is, after all, what the smart folks read.

In short it is this closeted and very pleasant endogamy that proves so resistant to self awareness and change.