In the middle ages religion was a foundation of the people. With the exception of the upper class (and even then), most everyone had lives that were pretty awful (feudal system, barely could make a living, medicine isn't great, etc.). Religion (in Europe Catholicism) was that shred of hope that if they did well in this life that they would be rewarded (Heaven). If they were excommunicated they would essentially have nothing else to live for, especially since excommunication would most certainly make them go for Purgatory and be tortured for a long time prior to ending up in Hell. Therefore, because religion was a fundamental part of life excommunication would mean that they would have a worse life beyond their death (Purgatory and Hell) for all eternity.
Hi. Most people of the middle ages though excommunication was worse than death because excommunication means you are shunned. They would more or less be banned by their church, their family, etc. Everything they knew and loved would turn their backs on them. Imagine a life with no friends, no family...nothing. For some death seemed far less excruciating.
The U.S. government forced the Native Americans to move to reservations in exchange for protection from attacks by white settlers. In addition, the Indians were supposed to be given a yearly payment that would include money in addition to food, livestock, household goods and farming tools. So basically white people were greedy for their land.
