You are right in your detailed analysis. This is exactly what the issue is and why the other guy was a bozo. And why I said earlier than anyone wanting to change this basic and worldwide Etiquette is off his rocker. You said it much more eloquently.What the everyday bow-stern guys want is to anchor close to the rocks w/o having to worry about swinging into them. Fine--but then get there first. If I'm anchored off the rocks at a distance that allows me a full 360-deg swing w/ rode stretched out, and some bozo comes in and fixes himself between me and those rocks inside my radius, he's made an error and violated boater Etiquette.
KG, in case some of the weekend warriors here "don't get it", I've thought it might be interesting to post your OP on cruisersforum and see their reaction. These "doubters" and psychologists may change their tune.
Stu