Most of the time, when we feel sorry for someone, these feelings are not as charitable as they might seem. Feeling sorry for someone is really a subtle form of condescension and defensiveness: "I'm glad I'm not you." You view the person from your own perspective.
Instead of feeling sorry for people, we should empathize with them. Draw from our experiences and our imaginations and try hard to see things from that person's point-of-view. Empathy means understanding the person, not necessarily agreeing with their opinions.