As long as they worship in a manner that does not violate the laws that apply to all people and all religions, then they have a constitutional right to believe whatever demonic nonsense they want to believe.
Are you willing to suffer a witch to live?
You are trying to separate Islam the religion and islam the government. They are the same.
The Founders would not allow a theocracy to flourish that was trying to use the Constitution to subvert our government. There were NO muslims that created our government. There were NO buddhists that created our government. There were NO hindus that created our government. This nation was built on Judeo-Christian values. Freedom of religion meant that you could be a Quaker, Presbyterian, Baptist, Lutheran, Catholic etc. The Founders would NOT allow an outside group to subvert and pervert the Constitution. The very thing YOU are trying to do.
"Posterity, you will never know how much it cost the present generation to preserve your freedom. I hope you will make good use of it. If you do not, I shall repent in heaven that ever I took half the pains to preserve it." John Adams