Nicely explained by Lacy K. Ford, the chair of the University of South Carolina history department, on the NYT's Room for Debate blog. The rage of Wilson and other South Carolina Republicans is what happens when the majority party in a one-party state realizes it's the minority party in the rest of the nation:
Republicans confident of their power at home suddenly grew very testy when confronted with impotence on the national stage. As the elections of 2008 swept large Democratic majorities into the U.S.. House and Senate and elected a Democrat president, the ability of South Carolina Republicans to influence the national agenda dwindled.
The 2008 elections suggested that South Carolina’s bet on a Republican national majority as the key to its continued federal influence had been lost. As the Republicans retreated into their shrinking southern redoubt, frustration, anger, and in some instance, unspeakable ugliness (the Wilson outburst) emerged.
Well, at least they'll always have Columbia.