people that have declared war on the US. Shall i go on?
But they can still use the phone... we can tap their phones and use info provided against them legally... threats of violence by a poster might be taken as inciting violence by the social media. Our laws guaranteeing freedom are being used against us by freedom's enemies, e.g. Islam. The same was true in my youth concerning communism; we were taught that communism was our mortal enemy - but we had to allow the American Communist Party the right to speak. If their speech broke any laws that was actionable, but otherwise...
We defeated communism (then) through force of effort and realities. We no longer seem to make the effort.