Aleph Beta: Shelach: Relating To A Vengeful God‏

In this week's parsha, we see the ultimate undoing of the people of Israel - the sin of the spies. When spies are sent to the land of Israel to scout the land, they come back with a negative report, and the people despair, leading to God's wrath, and the death of the entire generation over the course of the next 40 years. What was so bad about the sin, and more importantly, how can we connect to such an angry, vengeful God?