Why are Catholic Nuns so mean?

Iam writting a family book about our family from as far back as I can go. One of the questions I have is for the Catholics of the forums. Why are Nuns so mean? My grandmother, aunts, uncles, great aunts and uncles cousins ect ect, were mostly raised in the Cotholic Missions on different Indian Reservations. The one thing that I have found from talking to them and from past stories they have told me before they died was the Nuns of the Caotholic Missions were always mean and abusive to the children. My Grandmother has told me many stories of the evil nuns.
 One that stands out is the story of a boy who had become very ill. I don't think my grandma knew exactly what he was sick with but she told me that the Nuns had NO empathy for a sick child. The mission had boys dorm and girls dorm and behind the dorms outside was a small creek that ran behind the buildings and through the woods. The Nuns had been punishing this boy for not doing his chores and on that fateful night he was murdered by the Nuns. The Mother Teressa took him to the creek behind the dorms and drug him through the cold water until he died. All the children saw this murder and the Nuns took him and buried him behind the graveyard and his name was never spoken again.

http://www.unexplained-mysteries.com/forum/topic/199186-why-are-catholic-nuns-so-mean/