A few lines of reasoning I'd like to take on:
1)Crime was committed in UK, therefore trial in UK.
I don't understand net jurisdiction, but until someone comes on who does does, I think we should all clamp down on this. In the end, he stole information from an American database owned by the American government. Just like the page 1 Osama Bin Laden example, though the Twin Towers were blown up in America, Osama never set foot on American soil; all his plotting was done elsewhere. Can he then not be prosecuted for second degree murder just because he wasn't there himself?
Moreover, what if this were a real cyberattack that had taken place in (say) pre-invasion Afghanistan (or North Korea, or Iran, or...). Crime committed in Afghanistan, crime to be trialled in Afghanistan. And so what if the government is delighted by the whole thing? As you can see, it's alright to claim that the UK should run the trial when it's the UK but that's a bad precedent to set when the next cyberattack could be a real one that takes place in a passively unfriendly country. Of course, getting extradition in those cases would be hard anyway, but it's not helpful at all to set a precedent with your friends and then demand different treatment from your estranged eighbours.
2)US overrreacting. He's got Asperger's and he was only looking for UFOs!
Yes, he had Asperger's, he didn't do anything serious and he was a bit loopy. I'm sure this will be taken into account. The fact is, though, that a crime is still a crime. As stated in an earlier example, it's not as severe a crime to break into a store and not steal anything - but it still is. It's breaking and entering and it's still a crime. A crime you'll likely be punished less for, but a crime nonetheless.
We can't conflate the US's desire to put him on trial with the US overreacting in an effort to put him away until 107. There's a difference between understanding his Asperger's when he's on trial and giving him a free pass because he has Asperger's. When and if he's put on trial I'm sure the severity of his Asperger's and the role it - and other mitigating factors -played will be considered.