In this section, I think the most important quote we can use to analyze the relationship between black and white occurs in these words:
"He was sure burned when you wasn't here this morning. Come right in when we was eatin' breakfast and says, 'Where the hell's them new men? An' he give the stable buck hell, too."
This shows us that black people were considered a lesser class. The boss was mad at two white men. However, here we are given the impression that he took his anger out on the stable buck because of their actions. That isn't fair and it demonstrates the discrimination of the era.
Likewise, throughout the text, when the boss refers to the stable buck or when he calls him he uses profanity. We see "hell" here. A couple pages further in the book the boss says:
"Where the hell is the God damn nigger?"
The use of the term "nigger" was regularly used in the thirties. No one saw a problem with it... except maybe black folks who didn't get a say in how the word was used.
Thus, the relationship was one of outright disrespect for the human dignity of a black person. Being thought of as the lesser race, blacks were regularly degraded in the words and deeds of white people.