99% of people with corrosion problems always think it is the other guy causing the problem but on 90% of the corrosion surveys I do the problem is located on the boat with the corrosion. I am not sure why everyone thinks it cannot be a problem on their boat? But I always say make sure your stuff is right before pointing fingers. And I agree I would rather see a ground plate installed as a permanent setup. Also another misconception is that AC causes most corrosion, this is wrong DC is to blame. If you think about this it makes sense as AC flows back and forth so it will not move metal atoms from one piece of metal to another while DC is a flow in one direction and can carry atoms in a steady flow removing from one mass and plating another. When you plug into shore power the problems occur from the ground wire allowing DC current to flow. Think of the boats in a slip as cells of a battery and the ground wire connecting them just like a battery. This is why a ground isolator helps, it blocks DC flow in the ground wire but will allow AC to flow if there is a short.
Capt. Wayne Canning, AMS
Project Boat Zen - Boat and Yacht Repair and Restoration