How does Hiresh justify the existence of the caste system?

At its core Untouchable is a tale about class struggle. The paralyzing and polarizing differences between the various caste levels shape Bakha’s day and fuel the narrative. Class and caste play a role in every interaction Bakha has over the course of his day. When his hero Singh speaks with him in the morning, it is with a “grin [that] symbolized six thousand years of racial and class superiority.” I think the "justification" is that people know their station in life and class conflict is minimized. I don't think this is the reality though.