Do you have any background history of the dog you almost resscued? Breeding? How old was the dog? Was he abused? How was the dog guarding you from the finance, barking? growling? etc? As I said it can depend on that indivual dog. I've had a boxer try to lunge at me, yet they are supposed to be gentle. I also knew that this was because he was untrained by the owner as well. I also had a fixed male dane that would go after any dog and was distrustful of strangers. My current dane now is not like that and is intact. Other dog's had lunged and bitten him yet he's shown no signs of aggression. So you see it can vary so many factors can contribute. Even then sometimes when you think you've done everything right trouble still finds it way through. Just the nature of the beast. Have you tried contacting the breeder yet?