I understand the point; either its OFFINABUS or its not, therefore the middle ground yellow is indeed a bit of a cop out. I think you have to be careful however and take tone, aggression, direction, distance and context into consideration. If a player says "ah f***ing hell ref, I hardly touched him" in frustration, hardly looking at you, with frustrated, defensive body language, walks away ready for the free-kick to be taken and intends getting on with the game, surely we just get on with the game and a word in his ear about speaking to you and to be careful is enough? If a player says EXACTLY the same words; "ah f***ing hell ref, I hardly touched him" whilst marching up to you, veins popping, holding the ball, waving it and his spare arm about like a nutter, like he wants to kill you, preventing the game from continuing, in an aggressive, loud voice, this is a different matter.
Direct, personal silliness like, "you are **** ref" is different; its clearly aimed at you, is personal and gets a walk every time. I just think its dangerous to feel like you have to dismiss if you're sworn at. I swear in the pub, at work, at home, as do many others. Are you really offended sufficiently to red card every swear word? I'm just not and know exactly where I draw the line, a little bit of common sense goes a long way in my experience.