The two most prominent such groups, Media Matters and the Media Research Center, are starkly partisan.
Representing the left, Media Matters:
Pulling a collective Rip Van Winkle, the White House press corps has awakened from its extended nap just in time to aggressively press the new Democratic administration, just as it dogged the last Democratic president during his first days in office back in the 1990s. Conveniently skipped over during the press corps’ extended bout of shut-eye? The Bush years, of course.
And for the right, the MRC:
Shortly after the House on Wednesday passed President Barack Obama’s “stimulus” package, ABC and CBS commiserated with Obama over his unsuccessful efforts to woo Republicans.
Hard to be a watchdog when you have an agenda. Then again, if Nancy Pelosi can claim to be “nonpartisan” …

Ain’t no money in the middle. Brent Bozell versus David Brock – at least Brent has been consistent. Hard to believe they were on the same team at one time.
http://www.nizkor.org/features/fallacies/middle-ground.html
with a healthy dose of
http://www.nizkor.org/features/fallacies/guilt-by-association.html
“Extended nap”? Where as Media Matters been on vacation? This stretched credulity.