The authorities who detained Miranda do not understand why that is outrageous and probably underestimated the consequences of doing it.
The IC simply does not think that there are legitimate questions about either the legality of the programs that Snowden has revealed or the policy framework in which they operate. Furthermore, all of the professional political message men who write opinion pieces in various papers have been smearing Snowden and deflecting the discussion away from the policy questions for months. That is traditionally how issues like this have been managed in Washington and Washington expects those traditional mechanisms to work.
In other words, they very much believe their own bullshit, and they are used to operating in a world where their bullshit was the only kind of bullshit available.
Therefore, the IC does not see any legitimate policy discussion and they don't think that anyone else sees it either, at least not anyone of any consequence. They see traitors trading in stolen property. From their perspective, the publication of this material harms "sources and methods" and therefore aids terrorism. They literally think that people like Snowden are criminally liable for aiding the enemy.
So, in their perspective, Miranda is not far removed from a terrorist. He is a "loony" radical that is engaged in actions that undermine their ability to fight terrorism, which is not so different from actually being a terrorist.
Furthermore, they believe that they have an unlimited power to detain anyone at a border crossing under any circumstance and go through that person's data. If this loony radical who is engaged in actions that enable terrorism is going to appear at a border, they would be remiss not to exercise their powers to detain that radical and get as much out of him as they can. From their perspective, its all part of an appropriate anti-terroism program.
There are four problems with this perspective.
The first is that there are real policy issues that have been raised by the Snowden revelations. This has been repeatedly pointed out by independent policy experts who are largely sympathetic to the interests of the IC, but the IC has their fingers planted firmly in their ears about this. They are simply blind to it, and that lack of awareness of their own fallibility is itself a part of the danger that they pose.
The second is that lots of people know that there are legitimate policy issues that have been raised by this. People are not as reliant as they used to be upon oped columnists in newspapers to tell them what to think. People have access to raw material here and they can make their own minds up. Washington is not used to having to contend with situations where people aren't falling in line with the messaging that they are putting out. They don't expect it.
The third problem is that in a context where the public has a right to know something, classifying that information doesn't protect national security, it harms the integrity of democracy. In so far as there is a real policy issue here and Miranda is involved in the process of informing the public about that policy issue in a way that the public has a right to know, the fact that the information he is handling is classified is of little to no consequence. When the IC seizes his electronics and goes on a fishing expedition through them they are literally obstructing justice and the political oversight of their own institutions.
To make matters more complicated, the issue isn't black and white. Snowden and Greenwald have revealed some information which has contributed to a legitimate policy discussion. They have revealed other information which is of little political consequence and which actually harms anti-terrorism efforts. So, its really hard, perhaps, to have a clear view of this one way or the other, if you're being objective. Lots of people aren't objective and are only going to see the oppressive possibilities inherent in detaining a person engaged in legitimate journalism. For others, the matter may be more difficult to consider, which brings me to my fourth problem.
If this wasn't a border crossing, the detention and search probably wouldn't have been lawful. Its hard to speak to this issue from the perspective of British policy because I'm not an expert on it, but in the United States such an action, even if authorized by a warrant, would be explicitly prohibited by the Privacy Protection Act of 1980. In this country we keep police far from news rooms for fear of exactly this sort of conflict in which the two simply don't understand each other. In other words, we've explicitly chosen to favor the people's right to know over the government's power to keep people safe. Reasonable people in Britain may agree with US policy on this question, regardless of what British policy actual is. And regardless of how British policy treats the issue, that sort of balance should not arbitrarily turn upside down just because one happens to be in an airport transit lounge.
The recent and widespread abuse of customs authority as a giant loophole in society's careful, long term balance between police power and personal privacy and autonomy is, in my mind, a huge festering chest wound of a problem with civil liberties in the post 9/11 world. I have written about this problem repeatedly. The amount of international air travel that people are doing grows at a healthy pace annually, the amount of data that people are carrying with them across these borders is exponentially higher than it used to be, and the policy framework that customs officials around the world are operating under has changed substantially over the past decade. Defenders of this authority like to say that things have always been this way, but there is a mountain of facts that you have to ignore in order to comfort yourself with that rationalization. The idea that "anything goes at the border" means, ultimately, that you have no civil liberties at all, because you are going to be at a border with your data sooner or later. Therefore, if you value civil liberties, you ought to be concerned about this, even if you don't particularly like what Greenwald is doing.
RE: Greenwald's partner detained for carrying stolen classified docs