At Salon.com, Glen Greenwald describes it like this:

If even our Beltway media — rather, especially them — argues that criminality by government officials should not be punished, and that light should not be shined on what they do, then pervasive government corruption and deceit are inevitable. That is just obvious. And that is why [Richard] Cohen’s column so perfectly captures what has happened in our country and the truly indispensable role which most of our political press has played in all of it.

Our media stars have not merely stood idly by while our highest government officials engage in endless deceit and corruption. They actively defend it, enable it, justify it, and participate in it. Keeping the lights off is their principal function, one which — with rare and noble exceptions — they perform quite eagerly.

The occasion was the performance of the beltway media during the sentencing of Scooter Libby.  What had Cohen written?

With the sentencing of I. Lewis “Scooter” Libby, Fitzgerald has apparently finished his work, which was, not to put too fine a point on it, to make a mountain out of a molehill. At the urging of the liberal press (especially the New York Times), he was appointed to look into a run-of-the-mill leak and wound up prosecuting not the leaker — Richard Armitage of the State Department — but Libby, convicted in the end of lying. This is not an entirely trivial matter since government officials should not lie to grand juries, but neither should they be called to account for practicing the dark art of politics. As with sex or real estate, it is often best to keep the lights off.