No firing squad here. No electric chair and no lethal injection. This is straight up stoning. And boy is it invoked a lot in Deuteronomy (13:10, 17:5, 21:21, 22:20, 22:24). Some things that can get you killed (whether stoned or otherwise) are enticing other people to worship idols, kidnapping someone and selling them into slavery, and um, being a rebellious kid. No joke.
Because Deuteronomy is based on "The Doctrine of the Two Ways," it's not surprising that it's chock full o' death penalty—if you do bad things, you're a bad guy, so who cares if you die?
Today, many people argue that capital punishment is wasteful or barbaric, while others argue that the death penalty serves as a deterrent to crime. Why do you think this is such a bigger issue now than it was in the wayback times?
These days, almost everyone's in agreement that genocide is bad.
So what are we supposed to do with a book like Deuteronomy that instructs the Israelites to wipe out all of the other nations in the Promised Land? Read it for yourself:
When the Lord your God brings you into the land that you are about to enter and occupy, and he clears away many nations before you—the Hittites, the Girgashites, the Amorites, the Canaanites, the Perizzites, the Hivites, and the Jebusites, seven nations mightier and more numerous than you—and when the Lord your God gives them over to you and you defeat them, then you must utterly destroy them. Make no covenant with them and show them no mercy. (7:1-2)
It's strange to think that a book that offers us laws like "You shall not murder" (5:17) would speak of genocide. But there it is.
Some people explain it away by arguing that Israelites lived during a difficult period in history. It was a dog-eat-dog world back then, and everyone was just struggling to survive. There was no Universal Declaration of Human Rights, no Declaration of Independence, nothing. Only an emerging code of laws that began to take root among communities in the area. And the Bible is one version of that process.
We aren't the first people to think about these issues. There are thousands of years' worth of explanations, excuses, rationalizations, and philosophizing of these not-so-comfy Biblical moments. An example? Well, Deuteronomy 25:17-19 says to wipe out Amalek, right? The Jewish philosopher Maimonides believed that this verse did not have to mean a literal genocide of the Amalekites. It could refer to getting rid of immoral thinking in the world through proper teaching (source). Whatever works for you.