Doctors are no better or worse than any other profession out there. 80% of doctors are pretty bad, and the other 20% make the rest look decent. Just like any profession that has ever existed.
You should be double-checking absolutely every single thing a doctor is telling you - especially important things like giving a two year old psychiatric meds that are not approved by the FDA.
I do agree with your point that it's not the parents "fault" - but I also would be pretty upset with my parents if they blindly followed whatever advice some guy with a piece of paper told them.