The barbarity of Islamic social behavior has one source: and that is the bloody-handed, delusional, lecherous, but fabulously effective religious charlatan known as "The Prophet".
This barbarity comes down to the present day in three forms: the Koran; the Sunnah; and Shari'a.
The Koran (basic scripture), regarded as being directly authored by a spirit entity known as Allah, and thus intrinsically unreformable, is in many respects a handbook for abuse.
The Sunna (biographical account of the life, habits and practices of Muhammad himself) will be found to be full of crimes, perversions and atrocities, all presented as morally exemplary.
The Shari'a (legal code) based on the Koran and the Sunna, is an authoritative --- and in many unhappy parts of the world, enforceable --- formulation of thse barbarities into mandatory practice.
This has nothing to do with the genetic deterioration of various populations. It can infect people of any racial background in a single generation via constant propaganda and intimidation, whether they are the offspring of 50 generations of cousin-marriage or not.
The genome deterioration and subsequent rise in disability is a tragedy, but in the geopolitical context, a distraction. The problem is not Arab inbreeding. The problem is Islam.
That's certainly true. But the genetic impact is only another thing that reveals that the problem with Islam is that it is evil at its core, destroys everything it touches and produces nothing good.
I think that there should be preaching in Christian churches on a daily basis that points out the difference between the truth of Christ (and the Christian vision of life, which frees and makes creative) and the falsity of Mohammed's evil fantasy cult (which enslaves, destroys and brings darkness).