I'm not quite sure about that, people feel quite intimidated when they see how this government treats people like Snowden and Manning. I would argue that the self-censorship is one way to avoid being treated like them.
While I agree that the government is trying to intimidate people with their treatment of Snowden and Manning, I think the goals of the intimidating are very different. In these cases the people they are trying to intimidate are potential leakers, not average citizens. The goal is not to promote self-censorship, but keep existing government employees from leaking classified information.