Because establishing a good report with the American people, not losing a critical Cloture vote, and all-around not appearing vengeful during your first two minutes of power is more important than satisfying the DailyKos?
I detest Lieberman, but strategically it's a stupid move.
I like Lieberman, but both points are correct.
Even with 58 Senators, cloture may be possible in some cases. Honking off one of those votes is no a good idea. There is also 2010, and, barring something unexpected, Lieberman will be there.
After the appointment of Emmanuel, who is (unfairly, perhaps) regarded as an uber-partisan, it will sent the wrong message.