while this is a good argument, it does give the un-believer the chance to say "so they lied in the Bible" or there is something "false" in the Bible.
I can imagine though that murders such as this was very common back then. Every single nation committed this stuff and mainly because of how low human understanding was towards this. This was still in the age of the Code of Hammurabi. Regardless, it is a very challenging form of theological content that I think christians should be prepared to answer, especially at this age.
I don't actually think it's necessary to answer it. What happened in the OT
does not matter.
"No one can come to me unless the Father who sent me draws them, and I will raise them up at the last day." -- John 6
He went on to say, "This is why I told you that no one can come to me unless the Father has enabled them." -- John 6
My sheep hear my voice, and I know them, and they follow me -- John 10
When he [the Holy Spirit] comes, he will prove the world to be in the wrong about sin and righteousness and judgment-- John 16
What I have seen is this: The Holy Spirit does His job in convicting people of sin. However, what He sees as the "convicting sin" in their hearts is not necessarily the same thing we see with our eyes. They will have probably fully rationalized the sin we see with our eyes, thus our attempts to "convict the unbeliever of his sin" will probably harden his heart against hearing us. I have mentioned in another thread of a former prostitute telling me that very thing. That's why scripture says conviction is the job of the Holy Spirit.
But this is the truth: The Father has enabled people around us to be drawn to Christ. There are people around us who are enabled, and they are our "target market." Not everyone--just those people. Again, this is not something we can see, but because scripture says it, we can depend on it. It gives us confidence that our witness and evangelism (two different things, btw) are not in vain.
But only if we are actually speaking in the voice of Jesus, speaking His words of salvation, not condemnation:
“Come to me, all you who are weary and burdened, and I will give you rest. Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls. For my yoke is easy and my burden is light.” --Matthew 11
That's not the way most Christians in the US approach people, particularly those who look like grave sinners. Most Christians want to make sure those sinners are fully convicted first, make sure they know they're condemned and going to hell.
That's not the gospel. Condemnation is the voice of Satan, not the voice of Jesus. Those people who have been enabled by the Father need only hear the words of Jesus, and they will respond.
Nobody needs to be walked through the OT to get to Jesus. The OT does not need to be reconciled to unbelievers to get to Jesus.
What this means, to get to my point, is that debates about the Old Testament are distractions away from actually getting to the gospel. It's never necessary to get involved with them. Every minute tied up in those debates keeps us from speaking the words of Jesus, that Jesus is where those who have been enabled by the Father will find rest from the discomfiture that the Holy Spirit has laid upon them.
In the military, we have a concept called "preparing the battlefield." That means setting the stage beforehand so that your own side will have the advantage in a coming battle: Planting land mines, setting booby traps, stringing concertina wire, et cetera.
Rest assure, Satan has prepared the battlefield to prevent those who have been enabled from hearing the voice of Jesus from us, to distract us, to delay us, to reroute us, to point us into dead ends and endless debates, because he knows that if the enabled hear Jesus,
they will respond.