@cicerone imposter,
I understand. But, if you dealt with much classified, you must know how much the classification system is abused. Stop and ask yourself, "Why, in a free speech society, would the government hide from it's citizens that their every phone conversation was being recorded without any judicial consent."
As an amusing example of how absurd the abuse of the system can be, I once wrote a document listing the inner and outer diameters of every tube in a certain type of assembly. The classification censors were okay with this but made me remove referenced to which tube went inside the other. The reason: a suit had once wrote in an archived note that the assembly could not be machined to fit. I know some people think I'm making this up, but it actually happened.
I guess it is fair to acknowledge Snowdon's act as illegal, but it is also fair to argue about it's morality. And I cannot see that he did anything immoral.