I will give you some examples and some quotations.
The most significant example of social hierarchy creating prejudice is the townspeople who ridicule Scout and Jem when their father defends Tom Robinson. It is clear that even if a resident of Maycomb wanted to side with Tom or Atticus, he would be targeted for discrimination himself. In chapter 9, Scout gets in a fight because classmates are making fun of her because her father is defending Tom Robinson. Atticus tells her:
You might hear some ugly talk about it at school, but do one thing for me if you will: you just hold your head high and keep those fists down. (ch 9)
Scout also hears this talk form her cousin Francis, and when her uncle Jack discusses the fight with Atticus, Atticus comments that he knows his children will suffer from the disapproval of the townspeople caused by his crossing racial lines.
What bothers me is that she and Jem will have to absorb some ugly things pretty soon. (ch 9)
In Maycomb, things are the way they are. People do not want change, and the pressure to conform is strong. Most people are very judgmental. Even if someone lower in the social hierarchy felt differently, he or she was not likely to speak up.