The idea that you can exclude American citizens because of their religion alone is clearly repugnant to the Constitution. If you can show a conspiracy or if you can show some overt act such as serving in the Army of a foreign power like Isis, you can probably constitutionally deny that citizen his normal rights.
It is not even clear that you can deny immigration to a class of noncitizens based on religion alone. God knows how the Supreme Court would rule, it is possible of they would look of the fourteenth amendment granting equal protection to "persons" and declare the practice unconstitutional. But one thing is very clear, you simply cannot deprive American citizens of their rights simply because they adhere to a religion.
Islam is not a religion. It is a political system much like Naziism and Communism.
The Constitution allows for the free exercise of religion, but in the case of Islam, the free exercise of religion means that they should be able to murder infidels.
That kind of philosophy is not compatible with America. Anyone who professes a fundamental agreement with the teachings of Mohammed should not be admitted into the United States.
All true. But my point is that Islam isn’t a religion under the meaning of the 1st Amendment, and if formally challenged, its claim to be one would fail.