Dr. Greene's Answer
Many kids do go through a phase of finding poop fascinating. The goal is not to make it more so by reacting too strongly to it. Usually, the best way through this phase is to smile and say, “Poop is yucky on the hands,” and then take him and wash his hands right away.
If poop smearing is done as an act of aggression or frustration, it can be a cause of concern and kids should be evaluated to see if there is an underlying problem going on.