Everyone's missing the point.

There's a criminal out there making death threats.  The same way ISIS, and Kim Jong Un make death threats against Americans for engaging in activities based on what a given American views as their right, as an American.

There is a criminal out there threatening American lives, presumably in the name of America.  

Using THEIR alleged patriotism (the threatener's) as a justification or pretense simply doesn't work under our laws.  

Our laws say that is illegal.  The threatener is a CRIMINAL.

But, now that I think about it, that's a pretty good angle to use to go against ISIS spokespersons and Kim Jong Un.  Declare them criminals for making death threats against American citizens.  Indict 'em.