Would we accept this argument if, for instance, someone claimed that because the CULTURE of the modern day Israel is geared towards isolating and annihilating the Palestinians, would we go back and say then that the Jews were complicit in the Holocaust? No. Of course not. If we have modern day crimes, let us stand on those charges. But attempting to tie us to a movement we actively despised and reviled, voted against, and then fought and shed blood and died for, a movement of reprehensible people with no respect for human dignity, that is what you're doing. You're attempting to lay the crimes of the slavery movement in America at our feet. Its unfair. We gave it up willingly and fought to end it. We deserve credit for that.
Now the modern day Republican party doesn't represent the interest of blacks, nor does any party. No party represents modern day interests of any community, because they all represent the modern day interests of corporations. That's a completely separate conversation, stances in the Civil War era have little bearing on that. To say that these parties are corrupted in modern society beyond all accountability would be an understatement.