If we work, rest and pray solely with friends who live in the same neighbourhood, we develop fears and prejudices about outsiders. But if we develop multiple associations, if we mix with people from different backgrounds, we soon realise that they too are all right. Our prejudices dissipate.
It is one hundred and fifty years since General Sherman burnt Atlanta and the American Civil War ended. Over a million lives had been lost and the Southern economy was devastated. Abe Lincoln had achieved his objectives: the United States remained one nation; amendments to the constitution ended slavery and gave all male citizens the vote.
But laws of themselves do not change attitudes. Many in the South are still smarting from the "recent unpleasantness" and refuse to accept the changes imposed upon them. Problems of racism and social inequality persist. Cultural norms, once embedded, last for generations. Change is necessarily very slow. Multiple opportunities to mingle socially and to work together on shared tasks are required if progress is to be made.
Apartheid in South Africa and Segregation in the USA failed. We should learn from these mistakes and eschew all laws based on race.