Killings are rampant in the Old Testament, and I'd like to spend a bit of time focusing on some of the more contemptible examples, including a few of the many involving kids. Here are two examples of God killing innocent children in the OT:
"And it came to pass at midnight that the LORD struck all the firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the captive who was in the dungeon, and all the firstborn of livestock. So Pharaoh rose in the night, he, all his servants, and all the Egyptians; and there was a great cry in Egypt, for there was not a house where there was not one dead." (Exodus 12:29-30)
"But of the cities of these peoples which the LORD your God gives you as an inheritance, you shall let nothing that breathes remain alive, but you shall utterly destroy them: the Hittite and the Amorite and the Canaanite and the Perizzite and the Hivite and the Jebusite, just as the LORD your God has commanded you." (Deuteronomy 20:16-17)
Here God personally kills thousands of children, and commands the Israelites to completely destroy six entire nations (children included). If God absolutely has to kill people, why not kill only those people who could actually take responsibility for their actions?
The standard Christian response is that God was "saving" the children from growing up in an evil society. There are two problems with this. First, remember that God is omnipotent and omniscient—he can supposedly do anything. Are we really expected to believe that the best way he can come up with to save these innocents is to massacre them? Second, this is in complete contradiction with another Christian idea: that God highly values free will and wishes for humans to freely choose him. By killing those children, God would have ensured that they had no choice whatsoever.
Later God promises to make Israel's enemies eat themselves and even their own children:
"I will feed those who oppress you with their own flesh, and they shall be drunk with their own blood as with sweet wine. All flesh shall know that I, the LORD, am your Savior, and your Redeemer, the Mighty One of Jacob." (Isaiah 49:26)
"And I will cause them to eat the flesh of their sons and the flesh of their daughters, and everyone shall eat the flesh of his friend in the siege and in the desperation with which their enemies and those who seek their lives shall drive them to despair." (Jeremiah 19:9)
Perhaps this is meant as poetic metaphor. Perhaps not. Either way, trying to reconcile this vicious, bloodthirsty being with the loving God of the New Testament is an exercise in futility. And here is yet another example of killing children:
"He went up from there to Bethel; and while he was going up on the way, some small boys came out of the city and jeered at him, saying, "Go away, baldhead! Go away, baldhead!" When he turned around and saw them, he cursed them in the name of the Lord. The two she-bears came out of the woods and mauled forty-two of the boys." (2 Kings 2:23-24, NRSV)
Christians say two things to try and soften the blow of this passage. The first claim is that these were not children, but young adults. This is simply incorrect. The Hebrew words used to describe these children are "na'ar" and "yeled," both of which mean "child" or "boy." While they were occasionally used to refer to young men, in this instance "na'ar" is accompanied by "qatan," meaning "small" or "young," thus ruling out any such interpretation in this case. This translation is accurate.
The second claim is that to "go up" was to die, and to mock someone's baldness was a particularly cruel insult. This may well be true—the question is, why should it matter? I don't care how shocking their ridicule was. Having 42 young children mauled by bears is a vile and ruthless way to respond. I'll end with this passage, one of the worst in the entire Bible:
"If your brother, the son of your mother, your son or your daughter, the wife of your bosom, or your friend who is as your own soul, secretly entices you, saying, 'Let us go and serve other gods,' which you have not known...you shall not consent to him or listen to him, nor shall your eye pity him, nor shall you spare him or conceal him; but you shall surely kill him; your hand shall be first against him to put him to death, and afterward the hand of all the people. And you shall stone him with stones until he dies, because he sought to entice you away from the LORD your God, who brought you out of the land of Egypt, from the house of bondage." (Deuteronomy 13:6-10)
First I'd like to point out that this command is not merely theoretical. It was essentially carried out in Exodus 32: following the creation of the golden calf, God forced the Levites to kill 3,000 of their own friends and family members.
I'd like you to imagine that you and your dearest loved one were Israelite relatives living at this time. Imagine that they came to you and suggested that you worship some other god. You would then gather up a crowd of people, and together you would stone them. Stoning is a slow and torturous way to die. They would be bloodied, screaming, begging you to stop, and you would continue to pelt them with stones until they were a crimson heap on the ground, their agony giving way to sweet death.
This is the true face of the God of the Old Testament. He does not merely decree gratuitous, barbaric punishments. He also causes even more needless suffering by forcing those who love and care about the offender to carry out those brutal judgments. Christians, if you find yourself trying to explain this away, imagine how you would react if you read this passage in the Quran, with "the LORD your God" replaced with "Allah." You would find it absolutely despicable, and this in itself would probably be all you needed to reject Islam completely. Truly, the best word I can find to describe the God depicted in this passage is monstrous.