During the first half of the previous century and to this day black people have been stereotyped as dim-witted, lazy, fond of chicken and watermelon other times as aggressive criminals and thugs.
Mixed race relationships were forbidden in some parts of the United States and could get you arrested and put in jail. A black man could be lynched for even looking in the direction of a white woman.
A popular form of entertainment were minstrel shows where white people dressed up and 'acted' like black people, portraying them as dumb and lazy.