Subman, of course the sites exist - half of them are military bases, almost all of which will have a brig or gaol of some form or other. Thats excluding the old WW2 prisoner of war camps.
Like Angus said, why would the powers that be allow people to just take a sunday stroll through the sites and put up photos on the web etc, if it were what liberty for life claim its for? To further discredit them, I draw attention to the insinuation that the germans based in the US are there for something other than military cross-training - not to mention the fact the site all but acuses them of being fascists and nazis...
As for why I said a civil war won't happen up there - well, take a look at it recently. Civil wars are most prevalent in Africa, where more advanced military hardware is non-existent. Give 100 men (and boys, lets not forget) their AK47s and you have a rebel army to challenge the 150 men of the national army, who are armed with their AK74s and maybe an old T55. In the US, a civil war would end before it began. If it truly came to it, a flight of B1Bs could take out a town and the civvies will stop.
Surely you don't expect the military to fracture though, do you?