Levi's response to me yesterday was spot-fucking-on:
I think it’s more important to keep Shrub and Dick occupied. First, you really need to impeach both; if we only impeach W, we could end up with another Dick as president. That turned out badly last time, no? Heh. Second, impeachment would keep them busy, and we hope, out of new mischief (read: Iran). That’s the main reason; keep ‘em on their heels until January 21st.
In other words, I don’t see it so much through a moral or ethical prism as I do a tactical and economic prism. Press them and tie up their resources. Besides, it’s not like any ground-shaking legislation is going to pass in the next seven months. If you can’t get anything useful done, you might as well prevent really stupid damaging things from taking place.
B Kliban had a great drawing to show how I see this: