Why was bama first amused ar the scene of the old man carrying a food packet by its string without touching it ? Why was she filled with anger , dismay and revolt later on ?

She was amused earlier as she did not know the reason for the old man's activity. She thought it was funny that he was carrying the packet that way.
However, after her brother told her the reason for the act, she was filled with anger and revolt as she could not believe that such an elderly person was being treated in such a way just because of their caste.