The whole problem is that referees have always interpreted the laws of the game rather than enforced them. The fact is that the law is very clear and that there is no justification for one player to put his hands on another player at any time and that doing so should always be a foul. Only by introducing these grey areas have referees given themselves a problem.
It's a unique thing about football, actually, that habitual tolerance of illegality. It makes things flow and increases the rough and tumble, but it also makes the idea of consistent refereeing a virtual impossibility.
Hmmm, not convinced that it is unique to football. Rugby, as an example, is filled with rule violations that are routinely tolerated, with the ball not being put in straight at the scrum being the most obvious of them. Same happens to be true in the American/Canadian sports I am familiar with. Interference in hockey, travelling in basketball being two other examples.
Yes, it's because everyone (fans and authorities) consider refereeing inconsistency to be a desirable feature of the game, when it is in fact a bug.
It's the same with the commonly accepted habit of refs "evening things up" or being less likely to give early bookings in high profile games, or shirt grabbing at set pieces being treated more leniently than in open play. Nothing at all in the laws about any of these things, yet we all accept them, for right or wrong. Then occasionally the FA will arbitrarily decide to clamp down on one of them, as they have with shirt pulling this season.
It does, of course, ensure that commentators and fans get to have their cake and eat it on a regular basis. One minute they are castigating a referee for failing to enforce the law, the next they are castigating them for being 'over-fussy' when they do.
If it weren't for the fact that referees are, to a man and woman, deviant sex criminals, one might almost feel sorry for them.