What is this "operating asymetrically"? And how exactly does that justify anything? Seems like I can say US is opperating asymmetrically, so it's ok to kill al

What is this "operating asymetrically"? And how exactly does that justify anything? Seems like I can say US is opperating asymmetrically, so it's ok to kill all US citizens (or at least people who voluntarilly became US citizens). And it will have just as much validity. Like none...