This isn't different than the Chinese govt demanding us citizens be surrendered who break Chinese social laws.
My argument makes plenty of sense and it's very easy to ingest - if you aren't a member of my country and receive no privileges as tho you're a member of my country then you shouldn't be punished like you're a member of my country. What about that are you exactly arguing against?
e.g. if a journalist (in the usa or outside) knows your employer (gov or private) committed crimes against the population and kept proofs of it inside a toy safe, that you can open easily just by fiddling with it, and the journalist motivates you to go fiddle with the children's toy safe to get the evidence, is it: a) you and the journalists high profile spy-hackers? b) you employer a criminal, and incopetent at security?
Seems like classical, straight-up espionage. The only confounding factor is that Assange wasn't (as far as we know) working on behalf of a foreign power. But these days, that's what spies are - not James Bond, but merely a guy who coerces and helps his assets to gain access to and then exfiltrate secret information. Espionage.