This is pretty freaky. If true, the US Military is banning access to "political/activist blogs" through its networks. The need to control information on maneuvers and other strategically sensitive information in a war zone is one thing, but this is controlling access to OUTSIDE, political speech and news. That seems entirely unAmerican to me.
Of course, if it only applies to liberal or progressively minded sites, it's fine and dandy. According to ThinkProgress, military personnel can still access Fox News and the National Review.