Biodiversity is not distributed evenly on the planet. It's distributed very unevenly. We've heard about sponge reefs and coral accumulations. They're distributed. They are obviously important to protect, and on that I think we're in absolute agreement.
There has been a tendency to establish marine protected areas in places where there is no conflict. Generally, in places where there is no conflict there are no fish and no marine productivity, so you're not going to make much difference. Why bother?
If you're going to use marine protected areas as a tool—and I agree that it's only one tool in the tool box—then they should be put in places where they make a difference, so that your investment counts toward the broader health of the oceans.