We can argue the humanity of hunting in general, but that discussion is, in my opinion, beside the point:
the fact that shark-finning is unsustainable and will almost certainly lead to the extinction of several species if left unchecked. In discussing sustainability, however--if we want to be culturally neutral-
-we can discuss the massive consumption of energy in the United States and the impact that has on ecosystems.
For the first point, its a question of viewpoint. An asian might find the habit of killing for "sport" gross or mystifying. "You mean you are not going to eat that?? Why kill it??". It all depends upon your viewpoint.
For the second point, I agree with what you say, but the critical point is that it has to be done through education, and not "because I say so". Or because I say its cruel and unusual or wasteful.
For the last point. Indeed. Its seen as hypocritial to take the moral high ground when pointing out the ills in the rest of the world when we (collectively) have so much to answer for in our history. "Ah, but we know better now, and so are telling you what to do" is a poor argument that rightly gets rejected by most of the world.