I promise you, if you call the police or FBI and report that your neighbor is suspicous because reads the Koran, they'll be polite to you, hang up the phone, and do nothing more about it but possibly get a chuckle out of the lunatic who just called.
I promise you, that's not how it works.
Paranoid snitches look for trouble. First they look for a sign: a Koran, an NRA sticker, whatever ticks them off.
Of course, they don't report it yet. They know the FBI would laugh them off. Instead, once they see your NRA sticker, they hone in on you. They watch for more "signs." Shouting, a rifle, late-night guests.
Then they exagerate what they've seen. A rifle becomes "carrying in all manner of assualt rifles and military weaponry at all hours." A Koran becomes "extremist anti-American Islamist propaganda ... I'm sure I heard them say 9/13..."
You see how it works?
Then they report their exagerated delusions, and you can sort if out from behind bars.