> do not see Assange as a journalist.
Sure, a "journalist" is somebody who works for a mega-corporation, preferably owned by a billionaire with political ambitions, and reports whatever the party that controls his outlet considers to be fit to print at the moment.
> he was guilty of a very serious offence
When somebody is caught on camera robbing or stabbing, the "journalists" always insist he is "allegedly" guilty until the court decision is made. These rules, however, do not apply to people who publish dirt on politicians.
> would agree it’s not appropriate to steal national security information and publish it
"Journalists" have done it many times though. And got prestigious awards for it. Of course, the situation is different here - his wasn't approved for anybody powerful and didn't benefit any billionaire with political ambitions, so no awards for him.