It depends a lot on your definition of 'good.' You'll notice that humanity has mostly treated the oceans as a 'commons' since we first figured out how to paddle out on it. Meaning we've exploited it for food and travel, more recently for other resources, all while dumping our sewage and industrial wastes into it, letting pollution fall into it, spilling oils from ships, and so on.
By 2080 it sounds like the oceans are in even worse state than they are in our contemporary world, and a collapse of the ocean ecosystems would completely frag the whole planet. So in that the Sea Dragon is trying to stop that, you could say that it is good; its actions make the survival of human civilization more likely.
On the other hand, so much human infrastructure and wealth is built on treating the oceans as a commons. If that suddenly becomes the private fief of the Sea Dragon, and the Sea Dragon has to permit any activity effecting the ocean -- fishing, shipping, letting impure run-off enter it -- the implications are huge. For starters it would severely screw Wuxing and Maersk, but it would also make pretty much everything more expensive (transport by ship is by far the cheapest way to ship most things), and then think how many major world cities developed because they are good ports? And having to actually treat and clean on the sewage and waist?
The Sea Dragon might save the patient, but not without amputating a limb or two (figuratively)
