Spiritual avatars have spoken over the ages about non-attachment being a necessary part of the spiritual path. We must not be puffed up by our successes, our good deeds or our personal abilities, nor are we to be so horrified by our failures that we try to hide them or blame others. We are to simply live as the best people we can be, whether or not someone is looking. To God be the glory, to walk humbly and lovingly, to seek God every moment - these are our callings.
But, some use non-attachment in regards to evil and darkness. They wish to justify abhorrent behavior. In "The Divine Within" by Aldous Huxley, he addresses this quite clearly. Here is a small snipet of what he says.
Nonattachment cannot be practiced except in relation to intrinsically good or ethically neutral actions; the idea that it can be practiced in relation to bad actions is a delusion, springing from the wish of the ego to go on behaving badly, while justifying such behavior by means of a high and apparently spiritual philosophy.
It seems to me, we must guard against our egos using non-attachment as a cover for our failures and bad behaviors, but also as a culture we must not simply look at wrong behavior as neither here nor there. We must not condone the evils going on and just walk on by.
People need to learn the basic ways that make life liveable. Bad behavior has to be reigned in and hopefully changed so the person can be restored. We cannot allow murderers, paedophiles, thieves, violent people, etc to roam the streets. We cannot continue to walk over passed out homeless people on the streets. That is not the place for non-attachment.