We do have prisons where we keep people without trial.
We don't, as far as I know, have entire prisons where we hold people without trial because they 'know secrets' and we are afraid they might tell them. In fact, I don't know of a single instance of this, outside of people who agreed to keep some secret but then changed their mind (snowden).
>>Though we're not scared of what they'd do, mind you; usually it's what they'd say that's the problem. Non-allied parties who know classified information they shouldn't are effectively infohazards from a government's perspective.
We don't, as far as I know, have entire prisons where we hold people without trial because they 'know secrets' and we are afraid they might tell them. In fact, I don't know of a single instance of this, outside of people who agreed to keep some secret but then changed their mind (snowden).