generation of the exodus

"The Ma'ah'peelim: Forcing Their Way Into the Promised Land"

Because of the evil reports of the ten scouts recorded in parashat Shelach, G-d decrees that the generation of the wilderness shall not enter the land of Israel. Nevertheless, the next morning, a large group of people arise early to force their way up the mountain toward Canaan and are smitten by the Amalekites and the Canaanites. These rebels are known as the "Ma'ah'peelim." Why were they not allowed into the land of Israel, and why were they punished so severely?