I doubt that most people of faith or otherwise, hearing a voice in their head telling them to kill any child, would assume that God is directing them. Of course, people are conditioned to kill in response to an authority less than an all powerful supreme being. An execution order from a Texas judge may be sufficient, or an order from the head of a gang in other situations.
I thought of all the fathers who, like Abraham and Isaac, grappled with the reality of their son possibly being sent to slaughter at the direction of a higher authority during the draft for the undeclared war in Viet Nam. I thought of the jingoistic "Chicken Hawks" who evaded the draft in the 60s and 70s, but years later encouraged young people to go off and fight in Iraq to rid Sadaam Hussein of his WMDs and in Afghanistan to capture Osama bin Laden.
Finally, I wondered if the U.S. government drafts my son a few years from now to fight in Absurdistan, will I potentially sacrifice him or encourage him to move to Canada or Europe?