If your point is that there have been racists in both parties, that's a valid point. However, the original article is, as you know, about "history."
The GOP was formed largely to end slavery. In contrast, as set forth, the founders of the Democrat party were were overt racists, supported slavery, and kept up that racist history well into the 1960s.
I'm not defending the racist democrats of the 19th Century, but wasn't another reason (for the regular guy) to vote for DP to get more democracy*, more freedom for states and less centralization of power?
*In the form of "Jacksonian democracy", started by Andrew Jackson and meant that magistrates that supports a certain party get jobs when a new Government with that party wins. This led however to corruption and inefficient bureaucracy.
