I don’t know how to respond to people like this. There is a lot of killing in the Old Testament, much of it commanded by God.
Allow me to take a different approach from a contemporary point of view. Two things: The Branch House Davidian in Waco Texas (which is a sad and tragic event.) And the issue of abortion.
*Branch House: There were women and children caught up into a cult. All being abused (I’d say all forms of it, sadly. Truly sadly.) But nonetheless, Federal Agents tried to fight off the people’s keeping mainly young women and children in that compound. Well, the way the man set up that place, he put explosives or tanks of Oxygen laying around, or munitions, etc. In other words, he made it worse for the government trying to save and rescue the young women and children from that man’s hands. And, with great sadness, the Federal Agents ended having found the children died from all the stuff that the madman put in their way. Which nonetheless was ignited by shots fired by law enforcement. Thus, it was not their fault. And not their intention. God never intends for souls to go to Hell. He doesn’t want them to die, especially in their sins. Remember, God see’s us more than we see Him. He see’s us with the greater potentiality of the fall, in sin. He exceeds time and space. So there’s something more than just this life, what were made for. And doesn’t want us to live in the dastardly place of Hell. And thus must sometimes fight off souls who have fallen so gravely they’ve taken, or take others with them in the same and like manner the tail of the serpent swept a third of the stars and angels with him.
*Abortion: The Church teaches abortion is wrong in all times and every case. If some medical procedure must be done on a woman who so happens to be bearing a child in her womb. And that operation may nonetheless mean the little human life may die as a side effect of that operation. It’s not an abortion, quite obviously. Since abortion is the direct and intentional killing of a unborn human being. And, since a medical operation (i.e. taking out cancer of the ovaries.) The operation is not an act of abortion. So the baby may die. And if the baby does die, it’s because the baby was helpless to the cancer anyways which the mother was being cured of. Which would also mean the cure of the mother also results for being the cure for the baby too. But sadly dies, because of the often difficult procedure to save mom’s life, and child’s life. It’s not intended the baby should die, but is a risk which does incur from an operation as a side effect.
So when God faces off evil men (and/or women), He is trying to save lives from sin, eternal peril, damnation, and punishment. But, He is affronting the evils themselves, rather than the people (i.e. God is fighting the cancer of sin, not the people He is trying to save.) And just like the operation to the Federal Agents, it’s never intended for innocence to die. But nonetheless in a fallen, broken, and human world proceed to be the consequences that come with the fall, not God.