Actually, it isn't. All of those entities you cite present themselves as "objective" "news" organizations (except maybe NPR). And therein lies the problem. FreeRepublic is a discussion forum. The question of whether or not it is biased is meaningless.
The left-wing have their forums to bash everything American, and they identify Free Republic as 'conservative', plus a lot of other derogatory unrepeatables, as well, which in effect are complimentary, coming from those pinko mentally disturbed lice.