I have three dogs in the household and when the rough housing starts to get out of hand with two of them, the third steps in to stop it. It doesn't matter which two or one it is, they all do it. I'm not sure that the golden was so much resource guarding the puppy, but maybe protecting it? I had a lab that took my golden under his wing and the golden would hide behind him when he was scared. As the golden got older the lab let him grow up. How is the golden if you bring him by himself to the dog park?
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD