Anyone who thinks most people are not selfish and 'evil' or more correctly capable of acts considered evil is very naive. It's sweet actually (genuinely) and shows a great deal more faith in humans than I'll ever have.
I think people need to believe they are incapable of extreme selfishness or acts of 'evil' because they need to believe that about themselves.
But in the right (or wrong) circumstances I think they'd realise different.
Everyone has their price. Everyone. And if someone truly believes they don't then I think if they were ever in a situation where their hypothetical price became a real offer (iyswim) they'd find out something distressing about themselves.
It's really easy to sit comfortably, fed and with shelter, and talk about your morals but morality is a luxury.
Am I, for example, a bad person or a realistic person if I say yes, I probably would do x awful thing for y fantastic benefit?
I could sit here and say god no, I'd never do that, how disgusting.
Just like I could sit here and take it to real extremes and say in a post apocalyptic world I would share my last slice of bread with a stranger's child.
But I wouldn't. Truth is I'd bash them over the head and prise it from their cold dead hands if it meant my own child would eat that day.
Being all kind and moral about hypothetical situations I'm never going to actually face is so easy. I can sit there and give the Good answer, safe in the knowledge I'm never going to be tested on it. Others will never find out what I would or wouldn't do and more importantlyI would never find out what I really would or wouldn't do.
Am I evil or am I realistic about human nature?
Rhetorical question btw, I know I'm going to be told I'm evil. I disagree. I think I'm just someone who is under no illusions about the true nature of the wild animal that is mankind.