Depends on what you'd consider makes someone a 'Truther'. I might be considered a Truther because I believe that the government did have knowledge of the attack before it occurred (in the form of report[s], though they hadn't percolated up to the level where they could be acted upon); this, IIRC, is why there was a big effort toward restructuring how intel (especially inter-agency) was handled after 9/11.
If he were being held in a prison indefinitely without charges, it certainly would.
The fact that he is being held in a medical facility for 30 days in order to evaluate his health is less concerning.
I'm not so sure here. I think there's a certain insidiousness that can come from using a hospital instead of a prison, in the form of "see, he's in a hospital, that's proof he's sick" -- and just because it's a medical facility doesn't mean it cannot act as a prison.
Yeah, the FBI was incredibly incompetent. That figures, because for a generation, the DOJ has just been the armed wing of whatever party held the Executive Branch. And naturally, all the wrong lessons were learned. Instead of cleaning house, no one paid a price. Except American citizens. They added layer after layer of bureaucracy, passed The Patriot Act, etc.