There can be another argument in this, leaks effectively only affect already open and democratic societies, since authoritarian regimes are considerably less vulnerable to them and even immune natural selection would actually play against you.

Leaks may very well not lead to some liberal pseudo anarchist utopia but lead to further consolidation of power, secrecy and more and more tougher reactions and control of information.

And while you might think that this won't happen it will, leaks don't play that well in the public when they start touching individuals especially when you can spin them as an attack.

Unconditional release of information especially in large leaks leads to the public being against the leakers.

Releasing some DNC emails/documents might be acceptable by the majority of the public, releasing all the documents including donor information and private information of simple low level employees, volunteers or anyone who has registered or shown interest in a political party would not be well received by the public even without any spins.