I don't think anyone believes that everything done by, or planned, or talked about by a government should be made public. I think one of the many points being made is that a lot of what is called confidential shouldn't be. In a democracy any elected official or anyone appointed by an elected official is in the end accountable to the public. They work for us. I think that once elected they forget about this to a great degree.
It becomes very easy to stamp 'confidential' on a report which should be made open to the public so that we as the electorate can make an informed decision next go-around. This is the intent of the mass leak, to show that yes some things classified confidential should be, and that many things are classed in that category simply because they would make the government uncomfortable. It is of interest to the electorate that the Secretary of State has ordered personnel to gather data on UN officials. It is my understanding that wikileaks contacted the US government and offered the opportunity to redact information, and that they were turned down.
The 9/11 analogy is actually a very good point. But let's look at it another way. Apparently there were weaknesses in our security systems. Students who came from countries historically associated with extremism were over-staying their visas and enrolling in flight training. There had been rumbles about this in the intelligence community. If someone had leaked this in July, then perhaps things would have turned out much differently.
But again, the Guardian knows where these leaks came from. The NY Times knows. Le Monde knows....why is it just wikileaks under fire?