The Two Faces of George Stephanopoulos
In his pre-pitch for an upcoming segment on the show, he referred to his guest, Gen. Michael Hayden, deputy director of national intelligence, who he referred to as heading up the controversial "Domestic Spying Program".
When he got to the segment, he did the generally standard dual sided intro saying "Referred to by its proponents as 'Terrorist Surveillance Program' and by its critics as a 'Domestic Spying Program'...."
Therefore, by his own definition, Stephanopoulos is a critic of the program, and thus biased. QED (although we didn't need any additional proof as far as I'm concerned).