Interesting; I'm actually one to make fun of even the most horrific of events, so I understand the draw of something like this--I believe my (Asian) wife and I might've cracked a joke or two while watching Tsunami coverage (boy, they're spending a lot more time on it Japan than in the States), though we both recognize it as the mind-boggling tragedy it is. And I don't think that the bit violates any indecency laws; anti-discrimination laws, I'm not so sure about, but not decency laws anyway.
That said, I don't think that this was very funny to begin with, and it sounded far more racist than just insensitive. There is a difference; "Ha ha, you died!" is insensitive, "Ha ha, I'm glad you died because I hate asians!" is racist. The former may be offensive to a lot of people, but the latter is just wrong.
And so while perhaps the FCC shouldn't fine these guys, I'm with that Hot97Sucks site--they're not trying to get the government to censor them, just punch them in the pocketbook and get their advertising pulled. This, I'd say, is entirely legit--if the station broadcasts insulting crap, then show them you don't appreciate it by not listening and making it clear that you don't appreciate companies who help them continue.
That's protest, not censorship, and is another form of freedom of speech. In fact, a boycott seems like about the only way to get anything done in the US anymore.