I just returned from visiting friends in Louisiana and East Texas. Both women are active activists in their own way. One is volunteering in various ways with the Katrina aftermath, and one is highly involved in animal rescue and fostering and placing of animals.
My "Katrina" friend is surrounded by people doing good and being a community and her outlook is that people are inherently good. My "animal" friend sees the worst that people can do to animals and sees people as inherently evil. This has become a second-nature thought for both of them.
Growing up I was surrounded by a dysfunctional, alcoholic, ethically-challenged, "the world is out to get you" family, and I was sure I didn't like people and ultimately wanted a job where I worked in isolation. After I went away to college and met different sorts of people and grew up and saw "good", my outlook changed.
So now when I see my students in class and they behave in a variety of good and bad ways, I rest assured in the fact that the "bad" behaving people can only benefit from being repeatedly exposed to "good". Even though this may be how they act now, that doesn't mean that will always be their behavior.