I will say that 60+ plus years of blacks' support for the Democratic Party hasn't done terribly much to improve their wellbeing- it's not like the Civil Rights Movement was some DNC operation, and the Civil Rights Acts received more support from Congressional Republicans than it did from Congressional Democrats.
The Democrats who voted against the CRA aren't Democrats anymore. A lot of the Republicans who voted for it would not win a Republican primary today. My mother's uncle was as much of a Taft Republican as they come but he voted for the Civil Rights Act and likely wouldn't be able to win a Republican primary if he were alive today.
Name something a post-Eisenhower Republican president has done that specifically benefited the black community. Name something that Nixon, Ford, Reagan, Bush or Bush did to make the black community as a whole better off.