Typical Hollywood depiction of 1860 America; always endeavoring to rewrite History.
The average black IQ of the period was in the 50's and 60's. The average white IQ was 100. Most blacks spoke no English and those few who did spoke it poorly. Because of their low IQ (in the idiot and moron range), blacks were prone to violence in that they could not function/cope in this complex society. The blacks are portrayed dressed as some English (white) gentlemen and ladies of the time, speaking English quite well.
It was a time of very poor hygiene, especially oral. The average person of 35 years age had few remaining teeth, and the ones remaining were in poor condition. Baths were infrequent, even for the well to do whites.
The character creation of a black well spoken doctor is pure fantasy.