There is a no kill shelter where I live that I go to often. They have a section of aggressive, never adoptable animals. Believe it or not, the majority aren't pits, rots, or dobies...they are German Shephards. German Shephards tend to be real territorial. On the same line, they are such intelligent animals, that training may be able to help them. My friend trains the police dogs, and I am just in awe at what those dogs can do. You really can train a dog that there is a time and a place to be protective.

Are they fixed? That may help too if they aren't already.