Thoughts on Sunday's sermon

Sitting church this past Sunday, the pastor spoke on Joshua 7, as he's doing a series on the book of Joshua.

In this chapter, we read about Achan's sin, which is supposed to teach us that our "secret" sins can have an effect on others, even if they don't know what we did.

Joshua had sent spies from Jericho to check out Ai, but while there, they got ambushed and lost some troops. When Joshua questions God as to why this happened, he learns that some of the Israelites have stolen goods and lied about it and need to remove the culprit in order to have God on their side in battle. So the next day, Joshua calls everyone by their tribe to question them. Achan confesses that he stole some valuables and money from the plunder and buried them under his tent. The men brought the stolen items, along with Achan's sons and daughters, livestock, tent and everything he had with him. They then proceeded to stone Achan and the rest, and burned them, placing rocks on top and it now known as the Valley of Achor.

Here's what I don't get - why did the Israelites feel the need to commit murder? Achan confessed and needed to be punished, but why couldn't God have just struck him down dead? Why kill of the rest of the family because their dad was stupid? I mean in Genesis, when leaving Sodom and Gomorrah, Lot's wife turned around and looked back and God turned her into a pillar of salt, but the rest of them didn't get punished for it. Why did the Israelites have to kill them? And they all partook in it, from how it sounds. Is it okay to justify the stoning because Achan stole and needed to be punished?

Josh equated that it's kinda like the death penalty - criminals being put to death for their crimes - which I agree is necessary for those who commit really heinous crimes. But still...

Just my thoughts on the sermon - insight would be helpful!