Re: Why did the medical staff snitch?
If a patient tells a GP something they write it down in their notes. If there is a credible safeguarding risk, either to the patient or to others then they are responsible for telling a designated competent authority - this includes social services, the police, the DVLA etc depending on the issue.
If they did not do this and an incident happened they could be found to be guilty of failure in their duty of care. The notes would be presented as evidence and the GP would risk being struck off, sued or even have a manslaughter conviction.
The GP will try to help an individual in the best way they can however there are issues with resources and often the patient's desire for help.
In another scenario, if a patient presented themselves to a GP explaining they had a strong sexual desire for young children. That they had watched them in the park and thought about kidnapping one and taking her home and just being near young children made them uncontrollably sexualised, would you consider this innocent patient to be a safeguarding risk and expect the GP to make a judgement in their 10 minute slot about whether it was important enough to inform an appropriate authority?
Would you change your mind if the GP knew that this patient was in the process of trying to adopt a child or become a foster parent? They're still innocent and they're seeking help from the GP for his fantasies after all.