Yes, it is both worrying and reassuring (depending on which side of the professional divide you fall) that a doctor can always be sued for malpractice.
It seems to me that people everywhere can bring a case against a doctor at any time, but that the chances of the plaintiff winning vary according to several factors (not least of all being whether or not the doctor was actually negligent or incompetent!). This ought to apply equally whether the doctor is practising in the rooms or in public.
My indemnity insurance / protection society does not protect me from malpractice, or indeed from patient complaints or suits. It does (I hope) aim to defend me should I ever end up in this situation. Then it is up to the justice system to decide the outcome.
The really 'sad commentary' here is that this state of affairs tends to make us all more likely to advise the captain to divert, and less likely to intervene to a level consistent with our skills.