It's right for God to slaughter women and children anytime he pleases. God gives life and he takes life. Everybody who dies, dies because God wills that they die.
God is taking life every day. He will take 50,000 lives today. Life is in God's hand. God decides when your last heartbeat will be, and whether it ends through cancer or a bullet wound. God governs.
So God is God! He rules and governs everything. And everything he does is just and right and good. God owes us nothing.
If I were to drop dead right now, or a suicide bomber downstairs were to blow this building up and I were blown into smithereens, God would have done me no wrong. He does no wrong to anybody when he takes their life, whether at 2 weeks or at age 92.
God is not beholden to us at all. He doesn't owe us anything.
Now add to that the fact we're all sinners and deserve to die and go to hell yesterday, and the reality that we're even breathing today is sheer common grace from God.
I could make the question harder. As it was stated, it doesn't feel hard to me, because God was stated as the actor.
My basic answer is that the Old and New Testaments present God as the one who has total rights over my life and over my death.
"The Lord gave, and the Lord has taken away; blessed be the name of the Lord" (Job 1:21). How he takes away is his call. He never wrongs anybody.
How would you state it to make the question harder?
The part that makes it harder is that he commands people to do it. He commanded Joshua to slaughter people, okay? You've got human beings killing humans, and therefore a moral question of what is right to do.
The Bible says, "Thou shalt not murder," yet God says to Joshua, "Go in and clean house, and don't leave anything breathing! Don't leave a donkey, child, woman, old man or old woman breathing. Wipe out Jericho."
My answer to that is that there is a point in history, a season in history, where God is the immediate king of a people, Israel, different than the way he is the king over the church, which is from all the peoples of Israel and does not have a political, ethnic dimension to it.
With Joshua there was a political, ethnic dimension, God was immediate king, and he uses this people as his instrument to accomplish his judgment in the world at that time. And God, it says, let the sins of the Amorites accumulate for 400 years so that they would be full (Genesis 15:16), and then sends his own people in as instruments of judgment.
So I would vindicate Joshua by saying that in that setting, with that relationship between God and his people, it was right for Joshua to do what God told him to do, which was to annihilate the people.
But that's much more complex morally than saying that God does it. He can cause a flood and kill everybody on the planet except 8 people and not do a single one of them any wrong. But he didn't ask anybody else to do that. It gets difficult when he uses others.
An example of this right now is that God has given the sword to the government (Romans 13:4). Therefore I believe the government has a right to take a rapist and a murderer and to put him in jail. Or to kill him.
I think capital punishment is consistent with Genesis 9 and consistent with God's character, because of the value of man: "The blood of a man shall be shed for taking the blood of a man" (Genesis 9:6) But that's very different than saying that anybody can go around killing people.
So God has his times and seasons for when he shares his authority to take and give life. And the church today is not Israel, and we are not a political entity. Therefore the word we have from the Lord today is, "Love your enemy. Pray for those who abuse you. Lay your life down for the world. Don't kill in order to spread the gospel, but die to spread it."