So I’d like to be quick at this kind of killing… And take no captives.

As for the OT I also used to think like Mr. Dawkins, that the God of the OT was a cruel, vengeful God. However, as Christy and Dr. Ben would surely quickly point out, I never believe anything until I read it for myself. After reading the OT I put my Bible down in awe of the love of God. I would say that Ps 139 sums up the entire OT: “His love endures forever…” (endures: “1. Suffer (something painful or difficult) patiently 2. Tolerate (someone or something).”) I couldn’t believe the way that God endured the Israelites who continually spit in his face. I mean when you read the book of Judges you’re thinking do these people have dementia? Alzheimer’s? When you read the making of the golden calf while the cloud of God is ominously circling above them thundering on the mountain, after having just led them through the Red Sea you begin to understand that God’s enduring love is something way, way beyond anything of this world. When I thought about the depth of God’s patience and endurance and hope for the worst sinners who had spit in his face, continuously and how he just bore it though he could erase them in an instant, I really fell in love with God. I would argue that there is more love in the OT than the NT. One act of love is one thing, continual enduring love over millenia is in my book beyond anything in this world. 

This is a response from the Quest Study Bible on Joshua 6:21:

God does not delight in the death of the wicked (Ezek 18:32; 33:11). God wants them to repent and live. Still, the Bible implies a “point of no return” beyond which judgment is inevitable (Jer 11:11; 14:11-12; 15:1-2).

The Canaanite civilization was so thoroughly degenerate that it was beyond repentance. Chief among their sins was their idol worship, which included sexual perversion and the sacrificial slaughter of infants. Every level of their society was contaminated by evil. Left alone, that evil could have infected the community of God’s people. So God dealt with the problem, directly and forcefully.

Still, we are haunted by the killing of infants. Couldn’t the babies, at least, have been rescued? We don’t know why God included infants with the destruction of the rest of the corrupt Canannite culture. But because we know that God’s ways are just (Deut 32:4), we must trust God’s character in this severe situation. Also, we should remember that the physical death of a baby is not the same as eternal death.

Ben, you present two topics:
1) your friend’s question about Deuteronomy 13 
2) The Dawkins quote.  We need to think through each of these.

The question: “Hey Dr. Ben! I’m having some troubles understanding Chapter 13 of Deuteronomy, where God has commanded that people who try to sway believers from the gospel should be put to death? Did God mean this in the literal sense?”  Before we talk about what God meant, we must talk about what God said. I would respond to this first by asking, “Why do you think Deuteronomy 13 is God’s command to kill people who sway believers from the gospel?” 

This is not at all what Deuteronomy 13:1-18 says. You have to make multiple jumps to get from ch. 13 to that question, the way it is worded.  I suggest we read that chapter before commenting. 

I would presume the question is based on Deuteronomy 13:6-9?  “6 If your very own brother, or your son or daughter, or the wife you love, or your closest friend secretly entices you, saying, “Let us go and worship other gods” (gods that neither you nor your fathers have known,  7 gods of the peoples around you, whether near or far, from one end of the land to the other),  8 do not yield to him or listen to him. Show him no pity. Do not spare him or shield him.  9 You must certainly put him to death. Your hand must be the first in putting him to death, and then the hands of all the people.”

I propose that we follow the New Testament authors’ approach, who viewed the Old Testament in light of God’s grace. So for example, if we keep reading, we find that God is not commanding Israel to be harsh or narcissistic. Rather God wants his people to be full of grace and truth. They were not to hastily do such things, but “inquire, probe and investigate it thoroughly”!

“12 If you hear it said about one of the towns the LORD your God is giving you to live in 13 that wicked men have arisen among you and have led the people of their town astray, saying, “Let us go and worship other gods” (gods you have not known), 14 then you must inquire, probe and investigate it thoroughly. And if it is true and it has been proved that this detestable thing has been done among you, 15 you must certainly put to the sword all who live in that town. Destroy it completely, both its people and its livestock.”