Although Islam is probably the farthest of all the major religions from the truth, it offers a justification for those who already have homicidal impulses to justify their actions.
Their prophet, Mohahmed, was a pedophile and ruthless murderer.
The Koran, though sprinkled with enough phraseology from more credible sources, such as the Bible, to claim some credibility in debate, is basically a call to arms against those who believe in freedom and morality.
We can't outlaw it here in America, because unlike Muslims, we believe in freedom of speech.
We can however, show our disapproval, and take harsh actions against Muslims who call for their followers to commit crimes.
We can, we should, and we will.