Not a problem. We already have a precendent in the U.S.
In 1836 Missouri's govenor issued an extermination order against all Mormons in Missouri, based on nothing more than lies and innuendo.
The federal government at the time said nothing about this order being unconstitutional. To the contrary, the federal government was complicit and a willing participant in the actions against the Mormons.
Several years later when the Mormons were in the Utah terrirtory they sent an army to "keep an eye" on them.
Why can't we now do at least the same to a "religious" group that has a proven track record of violence and terrorism?
And you don't see a problem with that? People like you terrify me, I really hope you don't vote or breed.
Criminal actions are punishable in this country. Thoughts should not be. Making a religion illegal - even one as idiotic as Islam - is no better than the "hate crime" legislation we so rightly criticize.
Many of the things the U.S. Government did in the 19th century were wrong, like the genocide they attempted to perpetrate on the native tribes. Just because it's been done before doesn't mean it's right.