To argue that Lieberman should keep his chairs, particularly Homeland Security and Governmental Oversight, is to also argue that a member of the democratic party is unworthy of them.
I cannot think of why democrats wish to punish their own deserving members to placate the back-stabbing, media diva, and unpopular Senator from Connecticut. To keep him is to belittle his incompetence and will only embolden his intransigence.
Whether you are dealing with a wolf in sheep's clothing or a wolf naturally attired matters little at the jaws.
ADDENDUM: I just found out about a fun place on the web called Dickipedia. It is a Wikipedia-like encyclopedia of dicks. They have, of course, an entry for Joe Lieberman.