Maybe I've been lucky. The one time someone was dropping the hook too close and thought they were fine I proceeded to obviously video them in the process of anchoring. Next I asked them to please face the camera so that when my insurance carrier goes after them for the damage their boat will cause by anchoring too close, there won't be any doubt as to which vessel was anchored first or who the Capt was. They went below for a few minutes, came out and motioned that I was "number one"
before picking up their anchor and leaving the bay. Persons on another boat that also verbalized their displeasure during the anchoring fiasco applauded a little too zealously as the offending vessel departed.