As a non-American, I can only say: “pfffft”.
Why? Hmm, how to put it. After all the years during which I’ve seen all the arguing FOR the indefinite detention of non-citizen terror suspects, I would only expect the same law-surpassing reasoning to apply to citizen terror-suspects. They aren’t less dangerous or less valuable than non-citizens, and, well, “war is war”.
Lotsa people pooh-poohed the slippery slope arguments. Well, there you have it.