You’re right,their first mission was to suppress the black vote by any means-including murder.
Also, Democrats have supported abortion for a long time -- Planned Parenthood began as a eugenics campaign to diminish the number of blacks being born.
The Democrat Party is suffused with policies aimed at keeping blacks in a subservient position in society. They used to rely on paramilitary groups like the KKK, but nowadays they just use Congress and the White House.