Neither the British nor U.S. governments cares much what charges they can lay against Assange, as long as they can lock him up until they can decide what else to do with him, and how to get him convicted on charges of espionage, sabotage and, for all we know, extremely poor fashion choices.
Assange is a poster child for a lot of offenses, and appears to be guilty of at least some very serious ones. Let's focus on those.
He may be guilty of acting like a selfish jerk in his relationships with women, but doesn't appear guilty of brutally attacking them. Accusing him of rape for behavior that amounts to a violation of safe-sex minimizes both the charge and the stature of WikiLeaks as a focal point that should get a day in court to clarify who, when and under what conditions secret government data can be posted online.
The Brits and U.S. should get off the prurient charges and just get on with charges of espionage or whatever else they think they can stick him with. Given rules in the EU protecting the accused from prosecutions that amount to harassment, and the number of countries from which WikiLeaks operates, just figuring out where and how to set up an indictment will be a trick.