Is it possible for dogs to have issues w/a particular breed?

Hi there, I have a question about my 6 month old male puppy, maybe someone can help.  Our neighbors have four dogs that they don't do anything with, it's quite sad.  They have absolutely no training, they're always barking at people walking by, other dogs walking by, and cars driving by their house.  One of their dogs is a black German Shepherd and I think the thing has mental problems.  All day every day it's out there barking at my dogs, thankfully we have a ten foot tall fence but I still worry it's going to break through someday (one of their beagles has already dug a hole underneat the fence).  This shepherd is extremely aggressive towards my dogs and myself and boyfriend.  We go out to pick up the dog poop and of course the dogs prefer to go by the fence the most.  My boyfriend was out there picking up the dog poop and the shepherd came out and bit him through the fence.  It drew blood through his jeans!  Then a few days later I was out there picking up poop and the dog barked in my face the entire time.  We can't go outside and play or work with training our dogs without this dog barking at us the whole time.

So there's a bit of background to my current problem.  A few weeks ago both my puppies started obedience class.  The first class my male was the star student, the second week someone new had joined and his puppy was a black german shepherd.  My male didn't like him from the second he saw him.  There is another german shepherd of a more standard color in the class and my male doesn't have a problem with him at all.  Then the third class the guy with the black shepherd puppy didn't show up, but a lady with a black shepherd puppy was there, and my boy immedietaly did not like that one, either.  Both the shepherds are male.  In fact, my female is the only female in the class, and my male dog has no problem with any other male dog in the class (most the dogs in the class are intact, including my male).

So basically what all this comes down to is, is it possible my dog could have a problem with just black german shepherds?  He shows absolutely no aggression towards any other dog, only black german shephers, and I have a feeling it stems from the aggressive neighbor dog.

Of course we are working on this with him, he's learning to curb the aggression and he is so smart he learns so fast, but I don't want there to be any more problems in obedience class.

If you have any ideas please let me know!  Thanks!