Let me preface my comments by stating that Paul Kirk's decisive vote on the debt ceiling bothers me, and if I had my druthers, he'd be gone. But there is a larger issue here.
Although no date has been confirmed, it appears like Scott Brown will be sworn in around February 11th. Brown is trying to assemble his staff, get them housing, get himself situated, wrap up his state business, his family business, etc... Usually elected officials have two and a half months to do this. Brown has two and a half weeks. By all accounts, Paul Kirk has been extremely gracious towards Brown and his staffers. The transition process is underway and people are optimistic.
Scott Brown worked hard to persuade skeptical Democrats and Independents to vote Republican. His election has inspired a conservative resurgence in Massachusetts. The people voted for him, but it wasn't a vote against Kirk. There is little hostility towards Kirk.
Sometimes in the law there are no right and wrong answers, only arguments and better arguments. Legally, I'm sure there are many liberal attorneys that could make the case for seating Kirk. But the legal issues are secondary to the larger issue of disenfranchising a state, and that's exactly how it will be portrayed in the mainstream media. I can see The Boston Globe headlines already, "GOP Kicks Out Kirk", "Washington Republicans Leave Massachusetts With One Senator", etc ... But more importantly, it will just look petty.
There was something of a gentleman's agreement between all parties regarding a smooth transition. While I'm upset that Kirk was used as the decisive vote on one issue, most of his votes are irrelevant. It shouldn't be allowed to happen again, but Brown doesn't need to start his term embattled between the people of his state and national GOP forces, who don't care much about the people of Massachusetts.
Kicking a sitting Senator out and leaving a state with one sitting Senator is no small matter. It will leave a negative impression in the mind of many, including some of the Democrats and Independents who crossed over to vote for Scott Brown. Its a risk/reward analysis. Whatever is gained by Kirk's early departure will be accompanied by risk. Is it really worth the fight? Such a fight will take weeks to resolve, and Brown will be seated by then anyway. Why alienate people over a trivial pursuit.