I agree, no less than a plug caster needs to heed jetty walkers or chunk baiters need to heed boat channels and swimmers. It's the sportsman's responsibility to lay the line down for folks using the beach, IMHO.
On the other hand, I have experienced intrusions of the intentional and offensive nature from kayaker's in a steelhead river, boaters on the flats, swimmers wanting to swim in front of me while I was wading 100 yards from shore and working surface breaking fish and coming nearly to physical aggression over the matter (Sam, remember that ridiculous event?).
Courtesy goes both ways, either can be the offender.