Like Andrew Sullivan,
I think that the Obama campaign has little to lose and everything to
gain by encouraging the CPD to have Gwen Ifill to pull out of
moderating the VP debate.
It's not that the right's critique isn't utterly transparent, but media backlash was one of the principal dynamics in motivating the Palin bounce in the first place.
But there's another factor here too. In preparing for a debate, you are often preparing nearly as much for the "judge" or moderator as for the opponent. Both campaigns probably have a pretty good idea of what types of questions she is likely to ask, how he is likely to ask them. Palin and Biden have undoubtedly watched videotapes of Ifill moderating the 2004 debate between John Edwards and Dick Cheney.
By changing the moderator, you're throwing everyone a curveball, and catering to the candidate who is better able to adapt on the fly. Which, most likely, is not going to be Sarah Palin.