From the defense's point of view: this would not help their case one bit.
Good point.
Also, come to think of it, if the prosecution had brought it up, the defense could potentially use it to sow doubt into the jury's mind. As in this case is based on the government's paranoid fantasy of Aaaaarab terrorists using a man they claim is a white Soooopremisist, to attack an FBI office in middle America!!!
Read William Pierce's and Tom Metzger's comments on 9/11.
Arabs and white supremacists are actually quite congenial to one another.
Incidentally, a fair number of former Waffen-SS types gravitated to the lands of Araby in the 1950s to fight against Israel; some even converted to Islam.