Shots fired in Dallas of mohammed cartoons.

[Minimalist]

Whether to let a radical imam preach and recruit freely is a tough question

Not legally. 

In 1969, the court established stronger protections for speech in the landmark case Brandenburg v. Ohio which held that "the constitutional guarantees of free speech and free press do not permit a State to forbid or proscribe advocacy of the use of force or of law violation except where such advocacy is directed to inciting or producing imminent lawless action".[31][32] Brandenburg is now the standard applied by the Court to free speech issues related to advocacy of violence.[33]

http://en.wikipedia.org/wiki/Clear_and_present_danger