If you don't get the reference, that's OK. Neither did I (at first) and neither did CAIR's executive director.
It comes from an incident during the Battle of the Bulge in WWII where American General Anthony McAuliffe received a letter from a German Commander demanding his surrender.
This was the General's response:
Pressed for a further explanation (apparently "Nuts!" doesn't translate well), Colonel Joseph Harper (the man who delivered the message) offered his own explanation to the Germans:
So it could be assumed that 'NUTS!' was Allen West's way of telling the Center of American-Islamic Relations that they could 'Go to Hell.'
For more on Allen West's letter, go here.
For more on Anthony McAuliffe and the Battle of the Bulge, go here.