Just sayin', typically deer and seals are killed in quick, humane ways and the practice is very regulated and has numerous laws in place to protect the animals in question.
But, for the sake of argument, here's some questions to ask if you really are on the side of whalers and believe it to be a good practice:
Is there really any quick way to kill a whale, are humane techniques being researched?
Do ships face fines for killing young or juvenile whales?
Are they allowed to hunt during breeding season?
How strict a regulation is kept on the whaling ships and the numbers of whales they are allowed to kill?
Are the whaling communities actively participating in the regulation of whale hunting to protect the species (as in the case of deer hunting and seal hunting) and/or protection acts?
Is the whale meats being used to the full benefit of the community (last I heard huge amounts of whale meat were rotting away in storage due to lack of demand to meet the supply, sounds like a poor use of resources to me).
Is the whale populations being actively and aggressively tracked to ensure sustainability?
Are the whalers allowing independent monitoring of their whaling practices to prevent unnecessary cruelty or bad practices?
Is any scientific data actually being produced by these "scientific" hunts?
Is the public being educated on the possible dangers of whale meat?
As with any hunting industry there needs to be strict rules, regulations and protocols to follow. Personally I find the whaling industry to be a very slipshod excuse for a meat industry (especially since they aren't even officially a meat industry, they're operating under a loophole). Even if I did support whaling I still think it needs to be heavily monitored, much more so than deer or cows as the oceans is an extremely fragile ecosystem and it seems like not nearly enough research is being done to ensure the whalers impact on their hunting grounds is as minimal as possible.
Japan in particular is known for unsustainable fishing practices, why does anyone think their whaling practices would be any different?
Sorry but there's a whole bunch of reasons to not support whaling and precious few that make the practice seem even remotely necessary.