The breakdown of the black community in order to maintain slavery began with the breakdown of the black family. Men and women were not legally allowed to get married because you couldn't have that kind of love. It might get in the way of the economics of slavery. Your children could be taken from you and literally sold down the river.
If the technical innovations of the Impressionists led merely to a more accurate representation of nature it was perhaps of not much value in enlarging their powers of expression.