I don't think the question of what should be open vs secret is a very interesting debate, because the bulk of that answer is largely agreed upon. I think the more interesting discussion is answering this problem: How can a government have the ability to keep secret those things that are necessary, in a way that disallows (or minimizes) the ability to abuse that power to keep other things secret as well?
I agree that having an explicit statement that there may exist military and diplomatic secrets that are legitimate would help convince the people (like myself) who think his positions are too extreme to be useful.
"In some cases – tracking down organized crime, say – government officials have an obligation to keep their investigations secret at the moment that they are performing them." -- Julian Assange, in the linked article
Seems like a straightforward statement that he believes there are legitimate secrets for a state to keep, at least temporarily.
I agree that having an explicit statement that there may exist military and diplomatic secrets that are legitimate would help convince the people (like myself) who think his positions are too extreme to be useful.