Well...he was only 10. In my experience with young children, you have to explicitly say "Do not pet this dog because....." and explain it thoroughly. If you didn't do that then I would say it was your bad. You could have explained that the dog was showing avoidance by backing away and by forcing a dog who is doing that a person could be bitten. It could have been a good learning experience for the child that obviously doesn't understand dog language. I've seen adults force themselves on Jax when she doesn't want their attention. If adults don't understand, I think it's out of line to expect a child too.
The more I learn...the less I know