How do you respond to openly barbaric group that wants to commit genocide against you in a civilized fashion?<p>You can try to negotiate and they will kill your ambassadors. 
You can try to ignore them and they will slaughter your innocent civilians.
You can try to attack them and they will hide amongst their civilians.<p>What do you do.<p>When they openly tell you they want to nuke you out of existence, it is a matter of survival for not just you but for your civilization what do you do?<p>You have a button to kill the threat now or you can wait for them to get the button to kill you and you know they will have no hesitation to press it.