I don't refuse to feel sorry for or have compassion for anybody. Even with someone who has committed a terrible crime, that action is not the sum total of the individual's existence. Even "bad" people are capable of suffering, and I can feel sorry for their suffering.
People who "should know better" don't always make good decisions. We've all got a big reserve of unconscious motivations that can sometimes overpower good sense. We can't beggar ourselves to help someone who continually puts himself in trouble through bad decisions, but we can feel empathy and sometimes find a way to help that won't hurt us and that won't be wasted.