There isn't a line, there are poles. Even laws are interpreted by judges who have moods, and what not. Why quibble about imaginary lines in an instance where it's not anywhere close? Could such a line even exist? What is the precise length of the coast of any island? Depends on the resolution, and if you have high enough resolution it also depends on the precise moment you measure.

Can you name any "line", at all, in any sort of dilemma? Obviously it's okay for you to gently tip on the shoulder of someone blocking your way in certain situations, but in other's it's rude, not to mention "physically interacting" with them with more force and different intentions. Where do you draw "THE LINE"? Between being polite and being impolite, as well as being impolite and assault? How would you write the rule book to determine it in any situation for a minimum wage Facebook employee or algorithm so they wouldn't have to apply any of their own judgement? And just because you couldn't, just because nobody including God could, would you still refrain from judging even extreme cases with some certainty?