Family Dollar complaint: Harassing 13 year old boy

The manager of the store stated my son bumped into her. She then said, You’re not gonna say excuse me. My son didn’t respond to her, because he’s a child. He goes to register to pay for his items the cashier then said to him you’re not gonna say sorry he doesn’t respond. She then states you’re just all around rude huh? He still doesn’t respond.
My issue is they don’t have the authority to say anything to my son. They’re bullying a 13 year old boy.
I went into the store to tell her not to address my son please come and talk to me. She said gets irate and states I’m believing a child over an adult. I then state he’s my child.
While she’s being irate it was 3 more customers waiting to be served.
It looks bad on this franchise that she’s being rude to minors and adults.
That type if behavior shouldn’t be displayed from Manager, and Employees.