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.
Yep, pecking order.
I scolded my Pebbles (pscho Dachshund) the other day and as soon as I did, she snarked at up the "newbie" dog to our house, Meyer. He's fairly laid-back and really likes her, so he tolerated it without return snark.
But it's like...all doo-doo runs down hill?
Poop rolls down hill
I typed my reply before I saw yours...