@govietnam Dominance behavior and yes, I would put a stop to it. Humping is rude dog behavior and can become obsessive and excessive. My dog will also hump other dogs to dominate or if he becomes overly excited (not sexually, just excited). It's something I discourage and don't allow.
There are other ways to show dominance and he's just a puppy so this really isn't necessary to keep carrying on. You are also the owner so really should be the one in charge of both dogs so I think it's important to show both the dogs that you make the rules and control the situation. This way the older dog doesn't feel such a need to hump and the younger dog won't hopefully snap at he older dog as he gets bigger once he's tired of this behavior (or wants to challenge it). It's all about respecting each other.
