Many people know about the fluidity of politics, especially parties. Most presidents run on an extreme but "lead" as a moderate of their respective party. That is why I said it is insulting to keep repeating the OP as if it is entirely true without a shred of misleading information.
The fact that the party that aligned with Slavery wore the same badge as the political ones who claim to be for the progeny of slavery is neither here or there. That is just a change of moniker which happens every other political generation.
For example, today Republicans are seen as the party that seeks to bring back Jim Crow and/or slavery. The OP is a trope used very often to appeal to swing voters and black people in America during voting season. It has become so trite that it is now in the realm of repugnance - partly due to the audacity of such a sentiment in perfectly timed times.
The fact is that the last black person lynched in America was in 1981 in Alabama - when Alabama was considered a "ruby red" state. Blacks are still considered inconvenient by the republican party except to gain a vote - which will not go toward helping black people in America. But, they sure are useful entities when there is an election, or money to be made. This is blatantly obvious.
It would seem like an insult, at best, to blacks in America to continuously regurgitate the OP.