Olbermann didn't provide much context for the remark in the segment. Rosen is identified with the Denver Post, for which he writes regular op-eds, not KOA, and there's no mention of the debate in which the comment was made -- nor, surprisingly, the big whoop the audience gave after Rosen delivered his dubious bon mot. However, Olbermann did make clear his disapproval, asking how anyone making such a statement could call himself an American before closing the bit with a tone of revulsion.
Of course, Rosen, proud conservative that he is, would be more upset if Olbermann had praised him than criticized him. In the meantime, though, his ill-considered crowd-pleaser continues to linger in a most unpleasant way. Look below to see him top the Countdown roster.