The rulebook serves as guidance for the ref. Unless there are blatant textbook examples there's rarely an incident which doesn't give the referee some room to make his own decision that allows the game to run as smoothly as possible, which is the whole purpose of the ref in the first place.
Every other game you can see players going at each other and the ref booking them for it despite it clearly constituting violent conduct which means both have to walk. That's what sensible refs do, but when your boss is Mike Riley the goal seems to be putting the ref's performance in the spotlight rather than allowing the game to run its course
