The behaviour you mentioned above was not 'irresponsible', David S, it was caused by the position of the participants in the social heirarchy. They are powerless poors, and therefore are oppressed, lack resources and options, and therefore live in the fashion described. The 'blame', as always, lies with the powerful who made it happen that way, not the powerless who were mere victims.
Yes, the poor have absolutely no control over their own behavior. They're incapable of making personal choices. If one is poor, one can't control whether or not one only has one girlfriend or not, or whether one commits a crime.
Reality is that poor people are just as capable of making good decisions as everyone else. Maybe you need to consider the reason that many people like the ones David described are poor because they make bad decisions, not the other way around.