Southeast Asian here.
My family is also like that but it might be more of an ego thing than a saving face. You're not supposed to go around "airing dirty laundry" and you're supposed to give the impression that everything is perfect or even better than other people. You're supposed to act right, in a way that won't bring shame to your family. Bc o...... reply
"Only an idiot will fight with a 6yo kid."
1) "Huh. It seems that 6yo kids can only call people names and can't make actual arguments. Good luck with your few brain cells on the internet, kid."
2) "Goodbye. I'm not an idiot and I don't like wasting my time speaking to baby idiots so..."
3) [Just leave her on read and don't reply.]
4) [Send just...... reply