That is awful. It's like even the shelters don't know the breeds that well and their behavior. I have a pure bred ACD and he likes to nip me. He's not being agressive, he's a HERDING dog and they HERD things by nipping at them. He has never hurt me, but he likes to give little nips. He even will tug on my shirt so he can get my attention. It's sad he was put down so unjustly, I wish you could have saved him. I think some of the shelter workers need to be a little more educated about the dogs they are trying to adopt out.

EDIT: I know not all shelters are like this, but some seem to be very ill educated about the very dogs they are trying to adopt out.