If they had solid evidence that he was dragging women off the streets and threatening them with a knife then this is all reasonable. No-one is alleging anything like that.
I'm also throwing in an uninformed opinion that people are throwing 'sexual assault' and 'rape' around expecting a strong reaction, but I don't see the justification for getting worked up here. Setting aside any STDs (basically, assuming Assange doesn't have aids), the issue is that he did something that didn't hurt anyone, doesn't appear calculated to humiliate, was in circumstances where he might have misunderstood as having consent (given he was already having sex with these women), and can be rectified in 24 hours with drugs and a doctors visit. This would be grounds to discipline him, but not grounds to get worked up.