OK. American people kill whales because it's an American tradition. Unless you deem Native Americans not American.
Whaling and the killing of dolphins aren't cultural traditions for the majority of Japanese. Nevertheless, there are some regions in Japan that have been doing them for centuries.
Anyway, I don't know how these western activists can go all the way to Japan and paint Japanese a race that is barbaric, that is less than "Human Beings", and at the same time be completely oblivious to the cruelties in their motherlands.
Most Japanese people know what's going on with whaling and the killing of dolphins. And most of them don't want whales and dolphins abused. Still, the western activists aren't very popular because they reek of superiority and hypocrisy, at least that's how they look to Japanese people.
Edit: For the record, I scuba dive and I'd rather watch them than eat them. But I think these activists are really fishy. Dolphin meat is so uncommon in Japan, Daichi city is actually earning only $3 million or so a year out of it. In comparison, Greenpeace's annual budget for example is over $150 million. They can totally and easily compensate these fishermen for not fishing or try starting up whale watching businesses or something. It seems to me the activists are more interested in media coverage and the money that entails it than whales and dolphins themselves. And I'm not the only one who feels this way. Some people in the West share the same view.
The other Side of the Seal Hunt
The not so peaceful world of Greenpeace
I believe this view is more prevalent in Japan than in the West though. If you read Japanese, google グリーンピース or シーシェパード and you'll see what I mean. It isn't surprising really. They are depicting the Japanese as heartless barbarians. Of course the Japanese don't take kindly to them.