God told the Israelites to dispossess the natives of the promised land why? Oh, because they were, among other things, SACRIFICING THEIR CHILDREN BY FIRE. Guess what God told the Israelites? If you do the same things they did, YOU TOO WILL BE JUDGED. Judah did do it. And they were judged. We do it. And we will be judged. Sacrificing children is the abomination that causes desolation. God does the judging and avenging.
Your premise is that the response to child sacrifice by one group was to send another group in to slaughter everyone, including the children.
That is madness.