He called her a bitch!!

I took my son to the playground this afternoon, he was having fun and playing with this little boy and suddenly the boy's mom said we're going home and he said no Bitch!! I was shocked he was literally maybe a year older than my son who doesn't even know that word, and she got so angry grabbed him by his shirt and threw him down then said when I said we're going that means we're going, It was getting tense so I took my son and ran out