Er, MLK Jr. was a Republican.
60 years ago, almost all black Americans were Republicans. The Republican party was founded in 1854 as the anti-slavery party. In the 50s and 60s, the Democrat Party had rabid racists in it like George Wallace and Robert Byrd, who was then a Grand Kleagle and "Exalted Cyclops" in the Ku Klux Klan.
In the 1860s, Democrats fought to keep blacks in slavery. Later, they passed the discriminatory Black Codes and Jim Crow laws. Democrats started the Ku Klux Klan to lynch and terrorize blacks. Democrats fought to prevent the passage of every civil rights law beginning with the civil rights laws of the 1860s, and continuing with the civil rights laws of the 1950s and 1960s.
Over the last 30 years, the Democrats have been taken over by the Marxists, who have an entirely different agenda and have convinced Black people that--like women, gays, Latinos, and the disabled--they are a much-aggrieved interest group whose interests are best served by allying themselves with the nihilistic and cynical policies of the socialists. Read Antonio Gramsci.