I tell them to tell me if I am going to hit something, otherwise don't tell me when to turn. That is what the wife does. It seems everybody has their own hand signals and I can't interpret them from one to the other. I have 37 feet of TT and I do a fair job of backing in if I don't say so myself.
I think the good backing in people are a minority though. A lot of new RVers and less practiced people camping so I can understand a CG owner wanting to keep people from damaging anyone's property.