Like the f*cking social workers are doing such a marvelous job ?
They are trained investigators, since they never show up in time to actually prevent anything they should damn well investigate.
Now that I've vented my irritation at your liberal stupidity, I will reiterate, Cops are already trained in investigation, and observation, not social engineering BS. We already expect them to handle reports of violent activity, I don't know of any law that limits them to only assaults against those 18 and over, and that is what child abuse is.
They also spend most of their time dealing with scum bags, if this guy did this, I will bet he has some record for other stuff.