We had this thing called the Civil War & the 13th Amendment. The Jim Crow era massacres of Tulsa & Wilmington, lynchings & segregation was violence inflicted by whites on blacks, not the other way around.
When I asked a scholar of that period why the slaves did not take the opportunity to wipe out the slave holders, he had an interesting answer. The slaves were Christians & as such, did not wreak the vengeance that slave holders do richly deserved. It would have been a violation of Christ’s teaching to do so. I can’t argue with that.
What I meant was, how would secession and the establishment of an independent nation solve the demographic problem in the minds of the secessionists? Changing the government would not change the population numbers and demographic trends.