Just last month I had my heart broken by a golden retriever.
I have a friend who had one, and I always dog-sat Samantha when he went away and couldn't take the dog. He went to Austraila for a month, so Sam stayed here. I've known her all her life(5 years) and she is a nice friendly dog.
Anyways, buddy comes home and gets his dog back and life goes on..... till the next day when he call me and says, " This dog is dangerous now, what did you do to her?"
I asked him what he was talking about and he says that he got Sam home, and after she got through bouncing around greeting him, his wife and kids, ect, he put her outside in the yard. A while later he went out to do something in the yard and Sam was bugging him for attention, she wanted to play or whatever. He didn't and so he beat her down with a golf club.

As he was trying to get out from under his truck where she was hiding to continue beating her, she snapped at him(perfectly understandable). He lost it. He wanted to shoot her. "I can't trust her anymore" was his statement. He figured I had screwed her up by being too nice to her....

So he asks if I want to come out with him when he shoots her!!!!....Uuum, NO!!! I don't and I'll be over in 2 minutes to get her, DO NOT shoot her!!!
So I went and got Sam and brought her home. She was pretty timid and sore after that. She also went a little mean, I was the only one who could disipline her at all without her getting snarly. She used to get along with my dogs just fine, after the incident, she would attack then if they got too close. It totally changed her personality. I found a nice farm with no other dogs for her to live on and she's there and doing well right now.
But my friend had completely ruined this poor dog, through mistreatment. Any dog can be screwed up by a screwed up owner. Any dog can be a functioning, caring part of the family if it is treated properly.
I don't talk to my 'buddy' much anymore either.....
Now he has a young Shepard that he is raising to be another problem dog..... this poor thing is already messed in the head and things will only get worse..... it WILL snap one day and I just hope it's not one of his kids that takes the brunt of that.