The nations that will be destroyed:
Hittites
Amorites
Canaanites
Perizzites
Hivites
Jebusites
Israel was commanded to destroy these nations until they were consumed.They were not to make any covenants with them or show them any mercy. I thought that sounded harsh but the reason they were to destroy these nations was because they were worshiping other gods. They were putting graven images before God. They were just so wicked that there really was no choice but to kill them. There are certain instances when it is justified to kill just like Nephi was killed by Laban because he threatened the existence of an entire future nation. The Lord slays to bring about his righteous purposes.
I think it would be very interesting today to see what would happen because there is a lot of wickedness that goes on. I think it is very hard to stay away from these sins because they are all around us. But I think God gives us many tools to stay on the righteous path. As we have heard many times, we need to live in the world and not be of the world.
