The reality is that cousin marriage was very common the 1600s and 1700s in America, and it didn't really start to taper off until the 1800s. Anyone who's done even the slightest bit of genealogical research in colonial New England or Virginia, for example, knows you can't get away from it. Even among the upper-class Boston Brahmins, it was fairly routine. So the Americans who get creeped out and think, "Well, I'm not inbred" might want to rethink that one...
In any case, bohm gets it right. This is one of the classic accusations thrown at any "scary" group on the rise. And I have to say that if there's any country in the world with a clear agenda against Muslims right now, it's Denmark.
Also, I'm probably not going to get my information on this subject from a gold and silver forum...