I was recently talking to a mom who has been struggling with her teenage son's behavior. This past summer they sent "Carl" to spend some time with an uncle's family on a ranch. Carl told his uncle and aunt all about what rotten parents he had.
When my friend and her husband came to pick Carl up, they were unprepared for the criticism they received at the dinner table about their poor parenting. Nobody likes to have their parenting criticized and certainly not in a public situation. Needless to say, this experience has put a huge strain on those family relationships.
While it can be tempting to judge other people's parenting and set them straight, it is not a helpful or compassionate approach. In situations like these it's good to remember the Golden Rule - treat others the way you would like them to treat you.