Redirection? The GSD was corrected by the Golden, so took out his anger on the smaller dog.
Yes, I saw the redirection. My dog does this when I used to correct her biting (as a pup)at home. She would immediately turn to a dog toy, and take out her frustration.
With out being there my guess would be the dog was establishing rank. He was rebuffed by the golden so he felt the need to assert him self over the terrier to make sure his position as middle ranked dog was established. Again, just a guess.
I suspected this as well.
I found the behavior very interesting, and I wanted to learn more.