Obviously the owner doesn't care about the behavior of his dog, and what might happen if he doesn't teach it some manners. Have you ever been to his house covered in mud? Maybe he just things that the dog is only getting a little bit on you. Like it is nothing that is noticeable.
Perhaps you could get a local animal shelter agent to go to his house and talk to him about maybe taking his dog to obedience classes, or if he can't teach his dog some manners, then to keep it in HIS OWN YARD.

Hope this helps. Keep trying, you will find something out.