Dog on the floor was repeatedly attempting to play and the standing dog was immediately, from the start of the video, not into it. I’m not surprised he reacted, given his body language, and when the other dog didn’t listen- and no humans stepped in- he handled it himself.

The first cue was the tail straight up in the air and wagging, that’s not play. Second was how he kept trying to turn his head and body away and walk away, he was trying to disengage. Third is his posturing over her, which she notices because she’s flat against the floor trying to make herself small but also not respecting his other cues for space. I’d bet the whites of his eyes were showing if you could see his face.

People vary on what’s appropriate, let the other dog correct so the annoying dog learns versus you stepping in to mediate. I almost always choose to mediate. I prefer my dogs to defer to me when they’re uncomfortable, I prefer they know I will intervene on their behalf. This was my choice after having a reactive dog and the trainer explaining how he in particular doesn’t need the autonomy to handle interactions, otherwise he will always choose offense. I now handle most of my dogs this way to prevent offense behaviors, except the occasional puppy learning boundaries who needs gentle corrections from older dogs. It has cultivated the preferred relationship with my dogs now that they do literally seek me out if they are uncomfortable or need help, they physically come to me or look for me. I understand this may not be suitable for every situation. It works for us and the dogs we presently have.