"The act of engaging in criminal activity as a structured group is referred to in the U.S. as racketeering." = Wikipedia. Engaging in favoritistic kick backs of benefits based on membership in a class (in this case, Islam) is a crime. Replace "Islam" with "The Mafia" and you'll see what I am getting at. And of coure, Fannie Mae is in no way immune to prosecution if they are determined to be doing this, which appears to be the case.
These transactions are actually a worse deal for the borrower than a conventional mortgage, so your argument doesn't fly.