There are always exceptions to the rule. At the same time realize that it is a game created by a civilized society by people not in an apoc/post apoc world who can only really make guesses about human reaction. They are also restricted by different agencies from really going all out with the experience. I'm not saying there are no good hearted people out there, but if you were in a wasteland would you really take the risks involved in trust and end up on a pig pole? Or would you sit around and starve if you saw someone walking down the road with a bag that might have food in it? Its situational and depends on personal values but most people won't. These days its argued poverty creates crime. A wasteland is a world of extreme poverty, its a little much not to expect extreme crime as a result.
Actually you can make guesses. The entire world aint' exactly nice and squishy all over and even in places which are subjected to extreme poverty it's still only a relatively small number of people who can commit truly grievous acts of cruelty and not be haunted by it. I don't mean haunted by just feeling bad about what they have done, I mean seriously [censored] up for the long run and having trouble living with themselves. Morals and ethics can vary quite a bit by culture, but there are some things we are psychologically hardwired not to do and for most people, the emotional and psychological consequences of doing them are devastating. That's when you start getting into the extremes of such concepts as universal karma and cognitive dissonance.
Don't get me wrong. People can be monstrous when they are panicked, scared or threatened and do things they regret deeply, but it really takes one screwed up pooch to willfully kill and maim innocent person who is not an immediate threat and not be scarred for life. In general people will puff out there chest, yell, threaten and so-on at the drop of a hat, but in most cases they are ultimately just hoping you will run away before they do.