There are dogs whose temperments are just extremely sensitive. I know this from personal experience. My Tizzie was born in my house and never experienced any kind of trauma, punishment, abuse or neglect. Yet when either I or my husband picked up a fly swatter to go after a fly, she would leave the room with her head hung low and her tail between her legs. One could have easily assumed she had been hit, but because I lived every minute of her life with her, I know she never, ever was stuck, not even lightly. She was so sensitive, that all we would have to say was "I smell poop" and she again would look ashamed, hang her head down and leave the room. You never had to scold her, because she got the message from even a tone of voice that was slightly terse. Now just imagine if you have a dog whose temperment is this delicate to begin with and it has been abused, the effect would be compounded ten fold.