I'm assuming she's an AMA member (the mother) and I hope that the AMA is going to step in here on their behalf and offer more than "we've never heard of this happening before". This is the type of thing I give them money for...to lobby on our behalf.
It sounds like Dr meddling first, and I don't know how CPS works, maybe they are required to do the interviews whenever a Dr reports suspected abuse, but if this is what it appears to be at face value, then it would become gov't meddling if they choose to pursue it beyond the interviews. In my opinion, the ICU doc as way overstepped their bounds based on their personal opinions about kids riding motorcycles. The parents haven't abused this child and haven't encouraged him to do anything illegal. On the same basis, all children's MX would be child abuse and would be banned.