Let's separate Julian Assange and content of the leaks please. Ad hominem attacks are only meant to divert people from the content of the emails. Take them for what they are, not who rendered them to the public.
Assange being alt-right and the fact that he is going out of his way to leak material that improves the chances of the standard-bearer of the alt-right, Donald Trump, becoming head of state of the most powerful country on Earth are absolutely 100% linked together, and those links should be investigated.
Some information should not be public for a reason.
You're assuming that the goal is to expose something - that is, you're starting your argument with the idea that he's got some political agenda to achieve.
But he's stated that his goal is to weaken the powerful by making it so that they can't trust anyone to keep their secrets. In that context, any uncovering of a leader's secrets is work toward his goal.
You can argue that the costs of what he's doing exceed the benefits, but I think your claim doesn't support the argument you're trying to apply it to.