Personally I feel they are an invaluable tool for testing training and kind of cool just to see what you are doing. In a Race I feel they have no place.
If it was just a compass and or speed there is not much harm. With GPS however now you can have marks, laylines, start line etc. and now you enter into an area of assisted performance. This is the same as allowing on course coach boats, or radio communications. If they are allowed cart blanch for racing, it will not be possible to sort out who is using what and this is why electronics are banned across the board in certain classes.
Racing sailboats should be not be about power or electronics. Powered sail controls, artificial navigation etc and it is no longer sailboat racing, you might as well stay home and drive your Xbox