Is it imperative indeed. What about the individual who stole the...

Is it imperative indeed. What about the individual who stole the documents. That would be Manning, Already pardoned. Assange is just (one of) the journalist who published the leaked documents. The deterrent should be for those who commit war crimes, and that is not Julian. There is no harsh example where Manning is concerned. This is just about intimidating the free press.
There is no win here for the US. They committed the crimes. If they destroy Assange, in the eyes of many, they will also look corrupt, and unable to change from the criminal path Assange exposed. No one was charged over crimes exposed by Assange as far as I know.