Assange's original theory was that WL would create a "secrecy tax", making life difficult for evil orgs that had to keep secrets. But as far as I can tell, WL ended up damaging regular orgs more than evil ones. Because:
- minor scandals within regular orgs created large damage because the members have high ethical standards. While the members of evil orgs didn't care how corrupt their leadership was.
- evil orgs were more effective at keeping secrets, so most leaks were from non-evil orgs that didn't think they had much to hide.
That these second-order effects would end up dominating the first-order effects Assange intended wasn't obvious in advance, so I don't blame the guy for not foreseeing it. But at this point, we have to consider the "leaks in general are good" theory thoroughly discredited.
This depends on your own subjective view of which organizations are evil, and which aren't.
WikiLeaks' biggest document dumps were about the wars in Iraq and Afghanistan, and about American diplomacy around the world. The latter also revealed countless local scandals that were big news in different countries (for example, about corruption in Tunisia, which helped spark the Arab Spring).
I don't see any credible argument for the idea that WikiLeaks did more harm than good. What decisively turned American liberals against WikiLeaks was the publication of the DNC emails, which revealed a real scandal (the DNC trying to stack things against Bernie Sanders during the primaries) that had real consequences (the head of the DNC having to resign). American liberals turned against WikiLeaks for that largely partisan reason (the fact that Democrats were desperate for scapegoats after their election loss to Trump made the backlash against WikiLeaks even worse), while American conservatives wouldn't like an organization that leaks American state secrets anyways, so Wikileaks was left with no support in the US.
- minor scandals within regular orgs created large damage because the members have high ethical standards. While the members of evil orgs didn't care how corrupt their leadership was.
- evil orgs were more effective at keeping secrets, so most leaks were from non-evil orgs that didn't think they had much to hide.
That these second-order effects would end up dominating the first-order effects Assange intended wasn't obvious in advance, so I don't blame the guy for not foreseeing it. But at this point, we have to consider the "leaks in general are good" theory thoroughly discredited.