I'm sorry, but please learn to differentiate between a shitty day and overall sexism. When people are angry, they'll strike so that it hits the hardest, it just so happened that it was a woman and the derogatory term against her is 'bitch'. So, please, get over yourself, and report the incident as an incident, not as a case. Also, tell the kid to grow up, it might help him in life.
It's no different from how people don't like being told they're wrong, even if they objectively are.