It seems to me that democracy produces the idea of racial equality. In a monarchy, the idea of equality is absurd because one royal individual, his family, and possibly a group of aristocrats is inherently unequal to the broader population. The entire monarchal political system necessitates inequality.
In a democracy, however, political equality inevitably leads to social equality because every person is involved in the political process. Everyone must be made to feel both politically and socially equal for the system to maintain legitimacy. Even if voting is first limited to a specific racial category exclusion cannot hold because politicians will inevitably see the racial "other" as a source of quick votes, and the enfranchisement of the racial "other" necessitates their social equality by the logic of the system.
American history is an example of this process. Blacks became politically equal only because Northern politicians saw them as a way to democratically control the defeated South in the post-Civil War Reconstruction era. From this time forward, there were American social forces pushing for black equality.
Today, claiming blacks are unequal to whites is a challenge to the foundational logic of the democratic system. If racial equality is deconstructed democracy will be directly challenged.