Assange was involved in trying to hack. That’s where you cross the line and lose journalist protection under law.
Second the obligation of the press with leaks is to use discretion. He just dumped whatever he had that made Dems look worst including meaningless personal conversations of lower level ambassadors.
Finally he Endangered lives with his indiscriminate leaking. Iraqi spies had their identities revealed and had to flee.
I actually don't mind leaking spies, as you could argue that what they did, or at least the general philosophy behind it, does more harm than good. Spies fleeing is not the worst outcome.
I'm of mixed feelings regarding hacking.
It's the second issue that's the problem for me. He started acting partisan - leaking meaningless shyt just to make some people look worse cause of his grudge against Clinton, but holding onto shyt about Russia when Putin is ten times worse for freedom. He wasn't operating on any principles of freedom of speech or fighting the powers or anything like that anymore - he was just carrying water for a tyrant in order to get his own personal revenge.
I would have felt the same way if he had been picking on Bush or Trump. The USA is bad, but people who think that the USA is uniquely bad and that there's something better about the Russians or the Saudis of whoever (other than a matter of scale) are lost and aren't going to make anything any better.