They should learn that complaining is bad.
I would not agree with this. If people did not have the innate ability to complain about circumstances, not a lot of progress would ever be made.
A toddler will scream when its needs are not being met. Without complaining about circumstances by screaming and crying, how would the toddler communicate the will to be fed, or cared for?
i still go through this ( not food) but other things with my 2 oldest boys 19 & 17...whereas they question my authority at all times
bottom line for me is I provide the roof over there head, I pay the bills, I buy the food..you will do as I ask not as you please...
Once they are out in the world on their own than they can live by their rules
I don't agree with this either. They did not choose to be there, they do not have to choice to go anywhere else and are under your rule involuntarily.
Furthermore, is it so strange that they question parental authority? There are plenty of parents who impose rules on their children, and they do not follow these rules themselves. Sometimes they don't even notice that they are not following the same principles that they are demanding of their children, and children see right through this.