The poor prey on one another because their lives offer no hope and communicate the tragic message to these human beings that they have no possibility to attain a decent standard of living.

This quote means that people living in poverty become desperate and often take advantage of others, who are equally desperate. This is because their lives are so difficult, with no opportunity or hope of having a good quality of life. This creates a tragic situation, as these people feel that it is impossible for them to ever have a life with enough to meet basic needs.