Why would one believe such a silly thing? If I heard a doctor was accused (or even convicted) of shoplifting that wouldn't ruin the credibility of the lives they have saved. If Galileo was also a racist and a murderer that wouldn't reflect poorly on heliocentrism (although he probably wouldn't have a satellite navigation system named after him).

Even if Assange had violently raped and murdered multiple people (which would absolutely make him a terrible person) how would that affect the credibility of his civil work in any way? Does it make the truths that he helped expose any less true?