As it has been put to me, we have to have 'a contextual field.' How would we know hot if we didn't know cold - and the various gradients in between? How would we know colour unless we could experience it's absence? Absolute dark through to a white so dazzlingly we can't stand to look at it.
We put the label on an increasing absence away from love and at the further extremes we call it evil. Most of us know what it is in the abstract. But there are, of course, various shades of evil. Old Gautama the Buddha hit the nail on the head as far as the work we do as, 'Right livelihood.' Right livelihood is anything that makes the lives of ourselves and others around us happier; adds to our welfare' contributes to the common weal.
From this, we can deduce that ' wrong livelihood' is any type of work that does the opposite. But try telling that to the people who design and manufacture land-mines or napalm. They will justify it by saying "It's our duty to built weapons to defend our country." It is, of course, an evil. If others do it, it's wrong. If we do it, it's okay. But I stand with old Buddha. People know deep down, when all the rationaiizations are done, that they are making or doing bad things.
So we have a spectrum: the most heinous of criminal activity and crime that we can possibly envisage at one end, and unconditional, benevolent love at the other. But somewhere along the middle of this are the various shades of bad and good...based on our own conditioning.