You keep saying “very large number” when talking about the number of Muslims who are terrorists. I’m curious as to what you consider to be a “very large number”.
There are about 1.6 billion Muslims in the world. Here’s an analysis as to how many jihadists are estimated to exist — http://www.cnn.com/2014/09/26/opinion/bergen-schneider-how-many-jihadists/
Using the biggest number from that article as to the number of terrorists (106,000), and dividing it by the total number of Muslims, we arrive at an estimate of the jihadists comprising the fraction of 0.00006625 of the total number. Or, 0.006625% of the total. Do you consider that to be a “very large number”? Keep in mind that most of the jihadists are outside this country, and the percentage of American Muslims who are radicalized jihadists is considerably smaller.
You might also be interested to know that the vast majority of terrorist attacks in this country (as well as violent crimes in general) have been perpetuated by non-Muslims. http://www.huffingtonpost.com/omar-alnatour/muslims-are-not-terrorist_b_8718000.html. So if you consider 0.00006625 to be a “very large number”, you must consider the number of violent criminals among non-Muslims to be downright gargantuan.