Here's why:
1) We can keep more of our youth by agreeing to assume Harrington's MLE contract with Azubuike's (insurance-covered) expiring.
2) As a 6th man off the bench, Harrington can provide that bench scoring we're looking for. I know a lot of people hate on him, but he loved being a Knick, has a lot of heart, and the hope is that by playing with two clear alpha dogs in Melo/Amare, he won't try to bulldoze his way over 3 defenders and play within the flow of the offense. We know he has the skillset to succeed in D'Antoni's offense. He was also the key bench player on the 60+ win Pacer teams in the past.
But most importantly:
3) If we keep Wilson Chandler in any Melo deal, we can then look to S&T Chandler in the summer, since Harrington would fill the 6th man role in Wilson's stead.
There is a huge benefit to S&T'ing Wilson:
a) He's a RFA so if any team is interested in him, they have to work with us cause we can intimidate them by saying we'll match any offer. This is how Joe Johnson or Eddy Curry or several other RFA's were able to get their home team multiple picks and assets in a S&T.
b) If the team that wants Chandler is over the cap like Golden State was in the David Lee trade, they have to work with us in a S&T if they want Chandler. Result? They have to give up more assets cause we have the leverage. See: David Lee trade and Eddy Curry trade.
c) We could try and S&T Wilson for a coveted center whose contract would've been too large to work out a trade with normally. See: Marcus Camby's $11M contract. If we S&T Wilson starting around $8M, we can then use it to get Camby from Portland...or if Portland isn't interested in Chandler, we can look to acquire the assets that Portland would be interested.
End result?
Felton
Fields
Melo
Amare
Camby
with Douglas, Harrington, Turiaf off the bench (this is assuming we traded Gallo/AR for Melo, but hey, taking on Harrington may allow us to keep one of them as well).
All in all, hate Harrington all you want, but we should not be reluctant to take on his 5-yr MLE deal.