It's wrong to yell at someone else's children.
Karen and Jill have taken their kids to the playground for the afternoon; one of Jill's kids, Bobby, is throwing sand into the air.
Karen wants Bobby to stop throwing sand.
Karen points out Bobby's behavior to Jill, and she tells him to stop it.
Karen yells at Bobby to stop what he's doing, even though he's not her child.
Bobby stops, Jill explains why throwing sand is wrong; and Karen and Jill have a good afternoon together.
"Bobby stops, but tells Karen, ""You're not my mom!""; Jill gets angry with Karen for being bossy."