If someone approaches you to pet Bentley, I would immediately pick them up and say that he doesn't like to be pet from above. That way, you will have control over him and they can't try to pick him up.
I'm with you though, I never ever try to pet someone else' dog without asking permission. I've taught my kids to do it to and am always surprised when we get a surprised "thank you for asking".
If all else fails, tie a yellow ribbon to his lead and when people approach tell them that the yellow ribbon signifies a dog that people need to stay back from.
http://www.yorkietalk.com/forums/gen...ogs-leash.html