Here are the reasons to do it:
--AIPAC's annual policy conference is a feast of rightwing Zionist ideas, and many interesting Jewish ideas too. Inviting Walt and Mearsheimer, scholars of American Jewish history, would make it even more of a feast, and create the greatest buzz in AIPAC's history.
--Does AIPAC really think Americans like Israel like they like ice cream (as Stephen Spiegel said when he debated W&M)? Then show the strength of that conviction by inviting these two skunks at the garden party to parade their noxious and flimsy claim that the two countries actually have different interests.
--Walt and Mearsheimer are the shadow conversation. AIPAC knows this. Walt now has a very-legit blog at Foreign Policy. He's jumping up and down on the third rail, and will probably show up in the second Obama administration, methinks. Put your arm around them now.
--AIPAC faces a huge threat from J Street. It would with one blow deflect J Street, if not coopt J Street's very important message. As Agence France-Press said three days ago, of Walt and Mearsheimer's influence:
[T]heir criticism made its way to the heart of the US Jewish community and a progressive Jewish organization, J Street, was established several months ago to defend the goals of pacifist Jews before the US Congress.
--At a time when AIPAC's reputation is, well, clouded in mainstream life by its cheerleading the Gaza slaughter and other abominations, it would instantly invest itself with a kind of establishment intellectual nobility that only the Phil Weiss's and Jim Lobe's of the world would care to look through.
Reasons not to do it:
--AIPAC would be legitimizing Walt and Mearsheimer in a way that the Establishment has refused to do (Doesn't matter anyway; they're coming inside);
--Walt and Mearsheimer would win the debate, and be chaired through the marketplace...