Charles Blow has referred to black tea party members as part of a "minstrel show" for the white racists. That usage of 1920's imagery is at least a bit more tactful than what others have called them - though not by much.
The hate heaped upon black Americans who have joined the Tea Party movement is deep indeed. That said, the black tea party goers are anything but shrinking violets, they all seem to be well aware of the history of Democrats in the civil rights movement, and indeed, it seems a few are proud to be called Uncle Tom - the hero who stood up to the evil Democrat in Harriet Beecher Stowe's iconic book. As to their detractors, at least one tea party goer felt the proper moniker for them was Sambo - still dancing to the white liberal democrat tune.
And then there is this observation from James Taranto at the WSJ:
The political left claims to love racial diversity, but it bitterly opposes such diversity on the political right. This is an obvious matter of political self-interest: Since 1964, blacks have voted overwhelmingly Democratic. If Republicans were able to attract black votes, the result would be catastrophic for the Democratic Party. Even in 2008, the Democrats' best presidential year since '64, if the black vote had been evenly split between the parties (and holding the nonblack vote constant), Barack Obama would have gotten about 48% of the vote and John McCain would be president.
To keep blacks voting Democratic, it is necessary for the party and its supporters to keep alive the idea that racism is prevalent in America and to portray the Republican Party (as well as independent challengers to the Democrats, such as the tea-party movement) as racist. The election of Barack Obama made nonsense of the idea that America remains a racist country and thereby necessitated an intensifying of attacks on the opposition as racist.