When violence is committed by Muslims it is called "terrorism" (even when it is not--like when a U.S. soldier gets attacked while on duty in Iraq) and when non-Muslims commit violence that otherwise meets the definition of terrorism it rarely is called "terrorism." A lot of people have the idea that terrorism is committed almost entirely by Muslims because that's what we call any violence by a Muslim. (How many times do we have a shooting or bombing in the U.S. where the first question is "was it terrorism?"--a question that is ultimately decided based on the name of the perpetrator). I have no doubt that assumption would weigh heavily in Trump's decision-making when he decides what regions to ban immigrants from.