When Bakha has the urge to run away from the man yelling at him in the street, why does he feel he cannot run?

A crowd of caste Hindus gathers around while the man is yelling, and they completely encircle Bakha. Bakha knows that he is certainly physically strong enough to break through this circle, but he also knows that he will make physical contact with several people in doing so--and he does not feel that he can "pollute" them in this way.