This point came up in the comments to the earlier post on Lieberman but I think it deserves to be made more prominent.
Aside from the party loyalty issues, there are policy based reasons to remove Lieberman from his Homeland Security chairmanship. Homeland Security is probably the one area where Lieberman disagrees with the Democrats most. During the Bush administration he abdicated any of his oversight responsibilities. Why? Because he agrees with the Bush approach to combatting terror both at home and abroad. To the extent that this is an important issue (I think it is among the MOST important), Lieberman's continued chairmanship of this committee would be de facto handing this area over to the Republicans. This is not just about punishing a disloyal Senator. This is about policy. Lieberman can do a lot of damage Obama's efforts to reestablish constitutional government in the United States.
You can see a summary Lieberman's policy positions here. The ACLU rates him as having a 40% pro-civil rights voting record (which is classified as "mixed"). He's better on Gay-rights and affirmative action so the 40% must be so low because of general civil liberties votes. On foreign policy, Lieberman is famous for his "neo-con" positions.
Here is the section from on-the-issues.org on Lieberman's positions on Homeland Security.
- North Korea must know that we are prepared to use force. (Oct 2006)
- Iran: Sponsored resolution calling for regime change. (Oct 2006)
- Last thing we want is to release dangerous Gitmo detainees. (Jul 2006)
- The president has the right to act alone. (Jan 2004)
- Unwavering support for our troops in battle. (Jan 2004)
- Intelligence system must be reformed. (Jan 2004)
- Win the hearts and minds of the Muslim world. (Jan 2004)
- Right-size the military with Servicemembers Bill of Rights. (Nov 2003)
- Go back to the UN and negotiate about Iraq. (Nov 2003)
- Reform America's intelligence system post-9-11. (Nov 2003)
- Prosecute War on Terror, even if unpopular. (Sep 2003)
- 9/11 requires strength abroad to provide security at home. (May 2003)
- American military is best in the world; and has proven it. (Oct 2000)
- Don’t alarm America - the military is ready. (Oct 2000)
- Work with Iraqi opposition to overthrow Saddam. (Oct 2000)
- Supported use of force in Gulf War. (Aug 2000)
- Kuwait: Congressional authorization plus use of force. (May 2000)
He also voted to remove the requirement of a FISA warrant for domestic wire taps on two separate votes. Do those positions match up with what you think the median Democrat in the Senate thinks? What about the median Democrat in Connecticut? Or even the median voter in Connecticut (a state which voted for Obama 60.6% to McCain's 38.3%)? His positions on Presidential authority to "act alone" and his refusal consider shutting down the Guantanamo prison are sufficient, in my opinion, to disqualify him from the chairmanship of the Homeland Security Committee.