My view on this is that your dogs are establishing leadership rules. Dogs live in packs and naturally have a leader.
I believe that your older dog is putting your pup in its place to establish the leadership rules of the house - he is in charge not the pup. If you intervene and are telling the older dog off then you might be creating more problems as the pup may begin to think he is the leader and start to challenge your older dog more, which may result in your older dog getting rougher with him. I would just let them sort it out and let them establish the leadership themselves- unless of course the pup is in real danger of being hurt.
Good Luck
