The main reason the men of Ruby make scapegoats of the women in the convent is that they simply fear what they do not understand. Throughout time humans have feared what they have not understood, and more often than not, sought to destroy it.
Another aspect of their fear, I believe, is how well the women get along and manage to survive outside of the conventions of Ruby. Ruby is suffering from a rift between the young, who seem to take for granted all the founding fathers have worked and sacrificed for, and the old, who want to preserve their beliefs and practices. However, the women at the convent, regardless of race, age, and background, bind together for their mutual benefit.
One need not look further than the Salem witch trials to see how the strict Puritan religious code made scapegoats of the \'others,\' those who existed outside of the establishment and their religious code of behavior. Look also at how Hitler\'s Nazis sought to purify Germany of the Jews, who throughout time have been scapegoats for more than one culture. How the U.S. government rounded up Japanese Americans and forced them into internment camps during the second world war is another example of this kind of treatment.