Yusuf Qaradawi reveals that if Allah tells a Muslim to kill he must:
“No scholar of Islam or even average Muslim would ever say such words. If you believe that Muhammad is the messenger of Allah, then you must obey him—for he does not command except that which is good. So, even if he tells you to kill, you must— … The story about our prophet Musa [Moses], when al-Khidr killed the boy and Musa said “you killed and you did!” But then he [Khidr] revealed why he killed the boy, and why he punctured the boat. So we cannot distort the facts in order to please the people. Let the people be satisfied with the Truth [Sharia teachings], not the false.”
Interestingly, Allah has done just that!
And when the forbidden months have passed, kill the idolaters wherever you find them and take them prisoners, and beleaguer them, and lie in wait for them at every place of ambush. But if they repent and observe Prayer and pay the Zakat, then leave their way free. Surely, Allah is Most Forgiving, Merciful. (At-Taubah 9:5)