With the key word being "radical."
It is a statistical fact that the overwhelming majority of the world's Muslims are not radical. A fact which appears to be lost upon many from the right wing.
I fully agree that the overwhelming majority of Muslims are not radical, but studies show there's well over a billion muslims in the world, if even 0.01% of a billion are radical that still amounts to 100k. I know many muslims personally, the mechanic I take my car to is one of them. I like to believe in people, but when you're dealing with that many people the possibility still exists. I wouldn't call for a ban on muslims, but it isn't unwarranted to keep an eye on the activity that leads to violence.
I hate this is even a discussion, but we could probably equate it to the talk about gun control. The vast majority isn't an issue. it's really far to the edge fringe groups that cause the trouble.
Edit: When I say activity that leads to violence I don't mean being muslim. I mean those groups that provide the information to create bombs, or train people to assault areas violently. They exist and even as a vast minority they can cause large amounts of damage if not stopped.