Why?

It's clear that there is no Iranian fatwa against the production of nuclear weapons.

Scott Johnson at Power Line ponders the possible reasons why the Most Equal Comrade and Secretary Global-Test continue to talk about one:

 want to offer a set of possible answers that shade into each other, something like this: a) Obama and Kerry have been misinformed and don’t know any better, b) Obama and Kerry know better but are willing to say anything in a bad cause, c) to put it slightly differently, Obama and Kerry are doing advance work for the extraordinarily unpopular deal with Iran that they are about to deliver as a fait accompli, d) as Andy McCarthy postulates, Obama and Kerry cite the phantom fatwa as a rationale for making an unacceptable deal (“We needn’t worry about the inability to verify that the Iranians are not constructing nukes because the Islamic ruler has solemnly forbidden it”), and/or e) Obama and Kerry are willing tools of the Islamic Republic of Iran.

The case of the phantom fatwa persists. Its nonexistence cannot reasonably be in doubt. Obama’s and Kerry’s continued citation of it suggests either that they are fools, or that they know better and think we are.

How much weight do you give each of these?  To what extent do you think they shade into each other?  Are there other reasons?

In any event, it doesn't bode well for a post-American foreign policy that ought to be in the hands of responsible grownups, but isn't.