There's always moral instruction whether the writer inserts it deliberately or not. The least effective moral instruction in fiction is that which is consciously inserted. Partly because it won't reflect the storyteller's true beliefs, it will only reflect what he BELIEVES he believes, or what he thinks he should believe or what he's been persuaded of. But when you write without deliberately expressing moral teachings, the morals that show up are the ones you actually live by. The beliefs that you don't even think to question, that you don't even notice-- those will show up. And that tells much more truth about what you believe than your deliberate moral machinations.