Plantation owners in america often argued that the africans they imported were better off as slaves because they did not have the mental capacity to run their own lives. today, this seems both racist and crazy. how could such racist beliefs flourish?

Such beliefs justify social arrangements between dominant and minority groups that benefit those who accept them.

i believe the answer is: returns on investments, no wages

people who belong in upper class society would most likely get there by obtaining multiple source of income, which a certain percentage of ownership for businesses. since most of them are job creator, they would most likely get their money from profit, not wages.