But he's not being shielded from
any charges. The extradition request is for
questioning; he simply
hasn't been charged yet.
It's his story that, upon extradition to Sweden, the Swedes will turn around and hand him over to the US to be Gitmo'ed with extreme prejudice, but that's all it is thus far: his story. That said, it's certainly plausible; he's mightily pissed off the US government, which does seem to have a habit — particularly lately — of treating people that embarrass it rather less than gently. It would also explain how het-up the Swedes are to have him extradited, and the fact that Britain is willing to violate the Ecuadorian embassy (which, FTR, is not sovereign territory) in order to retrieve him. But idiotically zealous investigation of alleged rape (let alone lesser charges) isn't exactly unheard of, either.
Either way, however much good Assange has done the world by exposing the stuff he and WikiLeaks have exposed, he is an attention-whore, and his motives are pretty broadly suspect. Personally, I'd vastly prefer he not be subject to "extraordinary rendition" — not because of anything he's done, but because I don't think anyone should be shipped off to countries where they "interrogate" with rectally inserted broken beer bottles (to reference just one of the many stories that have bubbled up from that kind of thing). But that's just me.