I'd argue that seeing the world in black and white is what destroys people and civilisations rather more.
Many of the worst abuses of history have come from black and white thinking (people with black skin are not people, jews are not people, people without my political beliefs are not people).
That's a crap argument, and has nothing to do with morality that's base racism and can be just as easily phrased as some shades of grey. I'm getting sick of people twisting what people say into some racial thing when we are talking about concepts and morals.
Every time someone says "the end justifies the means" or "well, its really not that bad" or "I'm not cheating as much as them" makes the world becomes a worse place. Keeping your morals and doing the right thing benefit everyone.
"La Propriété est elle juste?" - Proudhon
Every society has a law like "no murder -- except sometimes, when you can".
And a law like "no stealing -- except sometimes, when you can".
And sometimes trying not to cause pain does make the world a worse place. Would you have police officers try their hardest to avoid causing pain? Criminals feel quite a bit of pain when they are incarcerated.
Nothing in the world is ever so simple as you suggest.