We place such a high value on freedom of thought and belief that we are reluctant to impose restrictions on anyone in the practice of religion, even when those religions prod their adherents to deny others of their own right to believe or to not believe.
Couple Islamic zeal in the pursuit of subjugating the world for Allah with the exceptionally high birth rates of Muslims and you get a worldwide disaster in the making. The fact that most Muslims never take up a cudgel against the infidel does not diminish the threat. Even if the silent Muslim majority does nothing more than aggressively increase the population of Muslims in the western countries where they live, their sheer numbers bolster the strength and bargaining position of the radical Muslims who are only too keen to seize leadership roles.
This is serious problem, and it needs to be looked at that way.
Along that line, whether islam is outlawed or not, or whether is koran is banned (or whether the parts of the koran which call for violence are deleted)...islam at the very least needs to be subjected to the full force of freedom of speech. The truth about islam needs to see the light of day and muslims need to feel free to leave that "religion" without fear of bodily harm.