It reinforces the idea that without equality in the US, the idea of a free society is a joke.
It's important to know that enfranchisement means the giving of a right, especially the right to vote. In this Douglass is saying that just to free African Americans is not enough. If they aren't given the same rights as everyone else, they are still enslaved. His repetition of "without this" emphasizes the importance of equality, not just the abolishing of slavery. Option B and C are simply incorrect statements. Also option D is incorrect because he knows that he will probably never have the support of all citizens.
