They're not. There has been plenty of corruption in African-American politics. Since I've lived in Atlanta I have seen my city's mayor convicted of it, watched a succession of city councilmen and school board members resign in shame over it. Even our sheriff shot his deputy, for the crime of running against said sheriff, and winning.
To a degree today's Tea Party rising in Georgia is a reaction against all that. They see the Clayton school district lose its accreditation, the Atlanta schools mired in a cheating scandal, and the DeKalb Schools run so badly the board has to be replaced. They have a lot to be angry about, and figure they, from their exurban lairs, can run things better than those who live and vote in the affected areas can. Thus we have the spectacle of the state trying to take over the city's transit system, which local taxpayers pay for, and basically sell it off to private interests, believing that private is always better than public, and never mind Halliburton.
But what has been most surprising about this crowd is how easily they're corrupted.