I always thought that sass was a sign of intelligence, since it requires a quick wit and a pretty good vocabulary (until it's mindlessly repeating things heard). Beyond that, the total inability to control what comes out of anyone's mouth (other than your own) is why I have always advised to ignore it. And that means actually ignoring it --not reacting, not complaining about, not glaring at them.
In a totally other context, you could talk about the human need for respect, and how the way we speak to people either builds their respect for us, or degrades it... including being cheeky and sassy and talking back. It surprises kids, the idea that how they speak builds or erodes their respectability --or how much people like being around them, or how valuable they are seen to be.
It is also very likely, at this young age, that he's literally bringing home what he hears on the world/tv and, as it were, seeing how it plays at home.
at 2:02 AM on Jan. 24, 2011