The plan is to disenfranchise black voters so they don’t actually vote while whipping up racist sentiment in the white working class so the proletariat is easier to control. Then, once there is an oversupply of laborforce on the market which is forcing prices down and thus the laborers into action if they want to survive, a portion of them can be redirected to commit race-riots against the other and not revolution. By killing off a large number of laborers the supply of laborforce goes down, hence the price of the laborforce goes back up and at whover survived wont have to take up arms again.

Readsettlers.org Chapter IV section 3 for instance to see it in action.