If he has secret video of US forces firing on unarmed civilians, yes, of course, I consider it an obligation of WL to release it and expose who covered it up.
If a diplomat sends a cable back to his superiors at the State Department and says, "The prime minister is rumored to act irrationally under stress. I suggest that we do not snap react to any statements he makes without obtaining further clarifications from other contacts within the administration." what good does that information being in the public domain do? It embarrasses the prime minister. It ruins the relationship between the sender and the prime minister. But what public good does it do to have this information in the public domain?
Sometimes I think WL revels in knocking the powerful down a peg or two whether or not they've actually done anything other than share a private thought that was now exposed to the public.
And part of my point is that I think Assange already picks sides. He's doling out punishment based on his own political biases. That's why I don't trust him.