Perhaps an over-simplification, but please consider the following analogy: You and your loved ones have a valid threat of bodily harm from a fanatic who has vowed to kill you. He shows up in your neighborhood. What will you do...wait for him to do something before you act? Obviously as a man of reason you would not run out in the street and kill him but you have an alternative... you have the option to remove this fanatic from a position of threat, until such time as he is no longer a danger to yourself or loved ones.
Personally I find this an acceptable option.
I'd insist that the police go arrest him (death threats are against the law) and provide what evidence I could to aid in convicting him. Next silly straw man?