you want to go from sustainable whaling using the most humane method possible to sustainable whaling using spears, massively increasing the whales suffering? I'd like to hear you justify that ...
Frankly, the suffering wasn't part of the consideration. Preservation of the resource over the long term in the face of human frailty is the primary concern for me. The squeamish can set up a garden plot and supplement their diet with legumes or whatever it is that vegans get protein from.
I do object to wholesale whale herd/pod slaughter by any means including ancient primitive techniques, and the practice of chasing an entire pod of whales or dolphin into shallow water and hacking them up one by one doesn't seem to be the right way to go about that sort of thing. I object to shark finning due to the mindless wastefulness of the practice as well as the environmental impact, since we don't really have good data on shark populations and their complete role in the ocean ecosystems.
If I was going to take a moralistic approach to "respecting" the animals, I think the rational approach is to draw a parallel between the demonstrated intelligence of various whale species to other animals we don't kill/eat for various reasons. For example, certain killer whale and dolphin behaviors are arguably the acts of a thinking creature with an intelligence level at least that of several "intelligent" species of monkey/ape/orangutan, while behaviors of certain baleen whales appear to be no more thinking than that of a cow, or maybe a horse. There is a moral and ethical argument against killing intelligent species for food. I choose however not to go there, because there is very little room for rational discourse in that area due to the hysterical rantings of extremists on both sides of the argument.
So I'll go for my own brand of humanist argument... If you're going to hunt down, kill, and eat, an animal that holds a fragile spot in the ecosystem, maybe an acceptable "human" compromise would be to accept some personal risk in order to make it VERY difficult to force that animal to extinction. If it is too easy to kill them, then the difference between a useful resource and extinction is a matter of policy and I don't trust people enough to think that's a good risk to take.