How to Fight Them
Then there are all those Koranic proclamations, and the hadiths, about killing infidels, which are enthusiastically promulgated in the radical mosques and the radical schools by the radical imams. That stuff is unacceptable, and we need to identify the imams who say it, and the textbooks that print it, and raise our voices against it. Even if all the courts in America said that they have every right to say those things, we are entitled to attack -- verbally -- those who preach them.
Second, we should prevent such people from entering America. By the end of the Cold War, there was very little prosecution of Communists, but there was a "watch list" to identify foreign Communists, and they weren't permitted to enter. Visa applications had a question about membership in organizations that sought to overthrow the American government, and so forth. We are entitled to deny entry to radical Muslims who want to subvert the Constitution and create a caliphate under sharia law.
Third, there is the "Al Capone strategy." The Feds could never convict Capone for murder, but they locked him away for income tax evasion. The radical mosques don't have to pay income tax, provided they strictly observe the regulations. Sometimes they don't, as it seems the Imam Rauf may have not. So the IRS should put its best green-eyeshade investigators on such cases.
And there is the possibility of taking away their tax-exempt status if a judge decided that they were dangerous. That status can be canceled if "the organization’s purposes and activities may ... violate fundamental public policy.”
Does calling for the destruction of the "infidels" conflict with fundamental American public policy? Maybe. We ought to make enough noise to find out, don't you think?