I personally don't subscribe to the idea that people or sane or insane. I would call that: desirable behaviour and undesirable behaviour depending on a particular society's conventions. However, if one was talking about the mainstream Western paradigm of sanity and insanity, the line is very slim.
As a film fanatic, I would use Stanley Kubrick as an example of whom people would call 'toeing the line'. He was supremely intelligent and intuitive, made great works of art that provoked and inspired, and was private, and had very specific tastes, for example: eating all of his courses at once. You can call this insane behaviour if you wish, but I would be first in line to punch you in the face if you implied that this behaviour was somehow undesirable, as some journalists did.
He's a man who doesn't comply by Western conventions, that's all. In some areas of the world, the idea of courses is completely baffling, and they'd call you insane for participating in it. Are they wrong or right? Neither, it's just desirable or undesirable behaviour.