For over 40 years the American right has defined itself and won elections, in part, by catering to white working-class racial disaffection in the aftermath of the Civil Rights Acts. 

Someone like Spencer or Bannon or Duke is the RESULT of all that careful Lee Atwater-type racist dog whistling. Receptiveness for their message has been conditioned into two generations of white people, who have been told that the reason for their declining standard of living and perceived loss of privilege is that supposedly lazy, undeserving, vicious people of color are living off "welfare" and driving up their taxes.

These people will bark like Pavlov's dog when they hear that alt-right message articulated explicitly.  It can no longer be assumed that the USA is "one nation dedicated to the proposition" of equality that Lincoln dreamed of. The USA has always been a white nation, where everyone else was admitted provisionally as long as they accepted white supremacy. This includes Obama.