I think the Dr. is overly harsh towards the step mom.

Of course X cannot choose her personality, but she has to learn to behave nevertheless (otherwise she'll become a sociopath or worse; throwing rocks at other kids - WTF?!?).

This answer doesn't sounds like coming from a balanced and wise therapist: it sounds like coming from someone who's biased and judgmental and, perhaps, still has her unresolved childhood issues (that would explain the harsh tones and words, and the emotionally charged language).