If the gap between rich and poor gets too large, and if those at the bottom feel they have no meaningful route to the riches at the top, then the fabric of society will fray, or even come unraveled entirely.
Utter hyperbole. As Smith and Hume said well over 200 years ago (in their backhanded fashion), it's the rich that provide the greatest service to society, fueling economies with their desires and silly whims.
Wheelan does temper his thoughts as he goes along, though, and raises many of the same points as de Botton, such as our peers wielding more influence on how we view our station than absolute figures, while acknowledging that television can distort one's peer group (it's almost like I *know* Tomkat, ya know). :-)