A popular level objection to Christianity today is to ask a Christian if Jesus killed little babies in the Old Testament. This banks on the idea of the Trinity and judgments recorded in the Old Testament such as the Flood or the slaughtering of the Canaanites. Another version of the problem of evil, the objection is that Jesus doesn't love people and is a baby killer. But this objection makes a number of mistakes that I will address here.
1. Who is God?
It may seem strange to start here, but this is where we should always begin. God is the maximally great being. Triune in nature, He is just, holy, righteous, and merciful. He is also love. So how could God judge? The issue comes down to thinking of God on equal footing with man. However, God is not man. Man is His creation - created in His image. But man is fallen. God however, is timeless, spaceless, immaterial, all powerful, personal, and all loving. To bring God down to our level is to misidentify the creator of the universe.
2. What is Murder?
Murder is rightly said to be the intentional taking of innocent human life without good cause. But, it is the taking of innocent human life by other humans. God is creator and the author of life and death. When God judges and takes life, He judges rightly as He is the standard of good. When we violate God's law, He is right to judge. When judgement befell man in the flood, God would have known several things: Noah was the only righteous man left, it would have been impossible for him to care for all of the children left. In wiping out mankind other than Noah's family, God was able to start over again to curtail the corruption that had overtaken the earth.
3. A Wrong View of Eternity
In the taking of the lives of children, God brought their innocent lives into His presence for eternity - to be raised up on the last day. We often think of life as only being the short time we have here, yet God has put eternity into the hearts of man. It is why so many cannot fathom there isn't an afterlife. We have an innate sense of it. But if this is the case, then why is abortion wrong some may ask? Reviewing our definition of murder, we do not have the ability or right to decide life or death outside of what authority God has given for keeping law and order. Abortion is the taking of innocent human life without sufficient cause. Because God brings an aborted child into His presence doesn't change the crime that was committed.
This objection is designed to bring the issue into an emotional arena, yet our emotions have nothing to do with the truth. Strangely, God judged the Canaanites for sacrificing their infants to the god Molech. In 2015, the total number of abortions performed in the US - including data from non reporting states - was 826,169. That is nearly 1 million abortions in 2015 alone. Yet the objection is claiming God is a moral monster for judging the earth and for killing babies. It would be good to find out if the person making the objection has an issue with this number.