As I understand it, they're not arguing for hunting any of the endangered whales, just the ones whose populations are healthy. As such, provided it's properly & sustainably managed, I don't see that it's any worse than fishing, hunting or slaughtering livestock.
Yes, whales do have an emotional pull that cod or cows don't have, but really is there any difference?
(note that personally I'd love to see the seas re-populated with loads of whales like they used to be, & I'd happily make an exception on emotional grounds alone, but I don't think that's sufficient reason to tell others what they should or shouldn't do)
Also, it might actually end up reducing the incentive to go whaling. At the moment it's seen as a contentious issue, so the countries that *want* to whale feel like it's an act of defiance, & most of them subsidise their whaling industries. If there was no huge opposition to it, & subsidies were removed, they might find that demand really wasn't that high; as far as I understand it, whale meat is becoming less popular in Japan anyway, & most of the other by-products, which were the reason whales were hunted to near-extinction, have been replaced by alternatives (whale oil lamp, anyone?)
It's weird how emotive pple get over whales relative to any other animals tho'... the Independent's headline was something to do with blood... nono, not expressing an opinion there at all. Given that most people are quite happy to spill cows' blood, or pigs' blood, I fail to see an enormous difference (well aside from the obvious enormous difference)