The readers, I believe, are supposed to be politically involved during reconstruction of the South and/or regular white folks who are possibly involved in the abolition of black suffrage. The gap is supposed to questions that nobody had answers to considering the race question. The gap was more of a rant that was set out to convince people that providing citizenship to slaves had created a stronger race aversion than what was already naturally embedded since way back when.
African Americans if allowed to vote, Morgan believed, would become more separated to whites and it was possible that they could create their own government with a mass anarchy. It was also possible that if black people became as status equal, then they would convince the general population that it was ok to interbreed.
Morgan uses fear when trying to convince his readers that African Americans could possibly abuse their power with obtaining voting rights.