Answer: discrimination
Explanation:
One of the reasons is discrimination and failure of equality. Some of the whites or others( not all) feel that the blacks are outcasts. They mark them as untouchables, they feel that( note: only some of them) they are superior to blacks and are born to lead. Maybe also because they think that God had created them as whites so that they will be superiors. But some of the whites had been protesting for black lives matter after the incident of the death of George Floyd, this matter has aroused their awareness that all people are equal and that the lives of each human do matter.
I am not criticising the whites and its not their fault, discrimination was present from ancient times. And still many people are holding campaigns etc to end these types of social nightmares. Not only the whites did show discrimination, even many other countries like India had shown discrimination, and labelled other people as untouchables. But there were many protests and many had raised their voices against these injustices like Mahatma Gandhi, and they were able to remove these types of social discriminations.
