Slavery in the 21st century? This isnt alternate history, this is just straight up fantasy.
How? Suddenly Southern plantation owners would become nice? The states where the overwhelming majority of whites had to have not treating blacks as subhuman and economically exploited only half a century ago--a century AFTER "slavery being bad" having to sink into their heads would've been ok? Do you think South African whites would've given up Apartheid short of war with a CSA backing them to the hilt and demonstrating how modern day slavery was still OK?