How do you ascertain someone is informed and rational? Where's the line between unapproved treatment and snake oil? I get your point, but the specifics are way

How do you ascertain someone is informed and rational? Where's the line between unapproved treatment and snake oil? I get your point, but the specifics are way more nuanced and difficult to get right than you make them out to be, even without getting into the ethical considerations of unproven medicine that extend beyond the individuals.