Reading the responses gave me another idea (I don't think any of the replies hit on it directly). Maybe the cops are interpreting his original post as a claim of child abuse; i.e. he's claiming he himself is abusing his children (he's trying to sell them after all). The cops have to investigate this hoax and therefore he's charged with falsely reporting an incident.
I'm not sure that this stands up though... If I come to you with hot dogs strapped to my chest and threaten to blow myself up. Then you - without my knowledge - call the cops, should I be charged?