You forgot Janice Rogers Brown, just appointed to the Federal bench. Mrs. Brown is an interesting case in point. She’s expressed the opinion many times that liberalism and welfare have destroyed the moral fiber of the black working class. Being a former welfare mother and member of that class, she certainly has a right to her opinion.
As a practical matter, Republicans win roughly half the time overall, and no blacks in the party means no representation. Also, when it comes to social issues, black Americans are fairly right wing. Gay rights, abortion, feminism, bilingualism, illegal immigration, Bible in the school and courthouse, you name it, black Americans line up pretty close to their white southern countrymen. Black Americans are also more likely to favor less restrictions on gun ownership than your typical white northern liberal.
That said, the Republicans have a well earned reputation as the home of genteel white supremacy, the white folks party. Even John Derbyshire, the conservative National Review editor admits that the Republicans are the go to party for Americans, white, Asian, Latino, who despise black people.
Looking at it in broad historical terms, black membership in the Republican party is an inevitable result of integration. Once you reject ethnic separatism/nationalism, the only other choice is integration. Integration will inevitably take place on the terms of the dominant majority. Since the white majority skews decidedly Republican these days, a big chunk of the action for black politicians will be in that party.
What’s really funny about Republicans, like Keys when he ran in MD, is the number of white erstwhile Republicans who will abandon their party rather than vote black.