Uncle Buck, true, Fort Sam is stateside, but that does not mean what he's doing is wrong, the SECDEF has made his ruling, location does not matter, it is allowed, he's the boss of such, that's it until he's overruled by his boss....
You are on track about "not supposed to be messing", if it's wrong, it's wrong, and should not be done. But for now, social media on govt computers is allowed.
Now, this does not mean work is put aside for surfing the Internet, the productivity has to be there. There is productivity and bandwidth monitoring, people do get shut off, counciled, etc......I've seen it.
Gun sites such as TFL are allowed, I don't surf THR.