My Grandfather had some wise advice for these situations. "When you have a bucket of **** , the more you stir it the worse it's gonna stink." When using diplomacy and being polite do not net results at least attempt the legal route.
With that being said some people are indeed impossible to reason with or get along with. In these situations keep in mind these types of people have a tendency to "self destruct." They make new enemies on a regular basis because they live to feud. Sooner or later they make enemies who will gladly go to war with them. .

Good advice. This thread is over six years old, though, so the issue has probably long since been resolved.