Barack Obama is a better man than I (am)

How can Barack Obama forgive Joe Lieberman? Isn't this the same Joe (not to be confused with Joe the Plumber, though both are equally opportunistic) who stabbed Barack Obama, nay, the ENTIRE democratic party (and his own constituents) in the back?
I get it, Barack Obama is a great man, capable of not only removing the knife out of his back, but also capable of forgiving the man who stabbed him. But, honestly, how do we know the Lieberman won't do it again? Personally, I have always found Lieberman to be a little stab-happy. How can someone go from the democratic VP candidate to a possible republican VP candidate?
I am a huge believer in tit-for-tat. Let us throw Lieberman under the same bus he tried to throw Obama under. We can wheel and deal for the other votes.
Bob Cesca says it for me on the Huffington Post.
The only other argument is that Lieberman brings democrats one vote closer to the magical 60.
I understand why that is important, but my question to you, imaginary readers, is if we demoted Joe like we ought to, would he really would jump ship? (I am stealing this from myself in a previous response to the issue) Because I don't think so. The republican ship is sinking and (I know I should stop with the boat references) though he is the galleys, jumping ship would be the equivalent to walking the plank.
He may be an independent (LMAO), god bless him, but he is still a liberal.