Keep in mind, Islam is not just a religion, it is also a political system. Criticism of political systems are not protected by our Constitution. Pushing back against the incursion of Sharia law is no different from resisting the incursion of Communism. They both are aggressive attacks on our Constitution.
And right now we don’t know how many Islamists are fundamentalist (i.e. following the fundamentals of their religion) and how many are just lukewarm like our main stream Christian church members.