Nelson Mandela was, in fact, a Communist. Winnie was a terrorist. He was repeatedly offered to be let out of prison if he would commit to eschewing terrorism. He remained unwilling to agree, so remained in prison.
I am confident Julian Assange is neither. I strongly recommend you better research Mandela prior to comparing him to Julian Assange, as Assange is a hero, who does not deserve to be smeared so.
Particularly considering the racist genocide now ongoing in South Africa, it is hard to conceive of a worse model to hold up as comparable to Assange.