"St Helena without Napoleon"
They're right; the worst part isn't the conditions (which, while appalling and barbaric, are pretty much par for the course in the US prison system), but the way that these people have no rights, no hope, and no way out. These people are detained at the pleasure of the President, and will only be released when he says so. Now what was that revolution back in 1776 all about again...?
And yes, we should all feel threatened by this. There are already three people being held as enemy combatants within the US itself, two of them American citizens. The government has deliberately labelled people as enemy combatants, shifted them to a military jail, and denied access to lawyers when their trial in ordinary, civillian courts looked like it wasn't going the government's way. It has threatened to do such to coerce guilty pleas from suspects. This does not bode well for human rights in America - and because America was previously the beacon everyone looked to, it does not bode well for the rest of the world either.