Hah, just had an argument with my mom over this the other day - I'm 23 (living separately), my sister is 12 (living with mom), and her and my mom were visiting.

Hah, just had an argument with my mom over this the other day - I'm 23 (living separately), my sister is 12 (living with mom), and her and my mom were visiting. I had just emptied a piggy bank and my sister (12 yo) was counting the coins. First my mom said "oi, those are dirty, you shouldn't touch them", and was promptly ignored. She kept escalating her rhetoric, finally describing the unimaginable diseases my sister could pick up. Still ignored, until she raised her voice. At that point, I stepped in, and the argument turned into whether or not I should question my mother's authority in front of my sis. Whether or not my sister learned it, I still think that questioning authority calmly and firmly is a great lesson. :)