Ouch. You pose some really tough questions.
I guess what I do is try to weigh things out and do things that are the greatest good for everyone involved. I'm human, so I'm not perfect at this, but I try to assist the survival of my fellow man and I try to be a good friend, loyal, trustworthy, etc. I guess this simplistic view keeps it from being so complex, it keeps me from being selfish (to a degree

), and it keeps things running more smoothly in my life.
I've been known to quit jobs out of principal, but as I get older, I find myself trying to work out compromises in situations, because there is no such thing as perfection. There are no absolutes.
There are lines, though. Cross certain lines and there is no way I'd be involved (criminal activity, for example). Or if one tries to be "too good," that's just exhausting and can cause problems too.
So I guess when it works best is when there's balance.