The video below is clearly biased on the side of liberal multicultural ideology, but it provides an interesting view of what goes on at ground level.
Sarrazin still speaks in terms of heredity and IQ, which weakens his arguments somewhat. While its true that Turkey (the biggest sender of immigrants to Germany) has a substantially lower average intelligence than Germany (90 vs. 102 points respectively), highly educated Muslims can be the most hostile to western culture, such as 9/11 ringleader Mohammed Atta, a professional city planner who was radicalized in Germany.
The problem is Islam and its relentless belief system of violent supremacism expressed in the Koran. One recent example of its power is the case of suicide bomber Moeed Abdul Salam who was raised by a Pakistani immigrant family in Texas active in promoting interfaith harmony and combating Muslim stereotypes. He appeared to be well assimilated as he attended an elite private school in Connecticut and graduated from the University of Texas. But he rejected life in the West to blow himself up in Pakistan for Al Qaeda. Were lucky he didnt bomb America.