Where did that article/report come from? Breitbart, or Stormfront?
Marrying first cousins were not unheard of in medieval Europe either. First cousins get pregnant easier than non-related couples. And, as long as you mix in new genes now and then, the risk for birth defects is just slightly higher for children of first cousins. Besides, just cause something is allowed, doesn't mean it's mandatory. (But that's probably hard to grasp for people like you; some fundies seem to think that if same-sex marriage is allowed, EVERYONE is going to marry someone of the same gender. Says more about themselves than they might want to divulge...)
Muslims succeeded in protecting ancient knowledge during the Dark Ages, when we in Europe were busy removing and destroying every sign of a different way to do religion than the Right Way at the time. They invented or spread the figures that we are currently using, so that we don't have to use Roman numerals.
Most Muslims migrate to nearby countries, where the culture and language is similar to their own. Wouldn't you? Lebanon, with a population of 4 million, has taken in about 1 million refugees. Immigration is a profitable thing for society in most Western countries. It costs a lot to bring a child to adulthood, and the ones who come here as adults are already ready to earn money and pay taxes. But, as the US doesn't have universal healthcare and soon probably don't have public schools either, this is probably less true there. Sweden (with a population of about 9 million) took in about 200 000 refugees in 2015. Swedish economy is doing great at the moment.
Around 1880-1910, a million Swedes fled from poverty and went to the US. They were seen as dirty, smelly and uneducated, but now their offspring are productive members of society.
Funny how an article that confirms all ones prejudices is very interesting, right?
Has he come yet?