Without an absolute standard, good and evil don't exist.
That's simple logical conclusion, factual and easily established. Either there is an absolute (read "non-debatable", "unchanging") standard, or there is no possible distinction between good and evil. All that is left is "good for me/you/us/them" and "bad for me/you/us/them". At that point, it's purely a matter of viewpoint: time, place, circumstances, and opinion.
Simple exampleAbsolute viewpoint: Lying is always evil (read as "wrong", "bad").
It may have some good results and truth may have some bad results, but truth is right and falsehood is wrong.
Humanist/modern/non-religious viewpoint: Lying is good sometimes, and bad others. Specific examples are "good" for some people, "bad" for others involved in the same lie. Everything is judged by the motivation and visible results.
We all speak in terms of "good" and "evil", "bad", "wrong", "right". These terms reflect a viewpoint that is no longer prevalent among human beings, and thus lose their meaning in such conversations. To me, it is always wrong to lie, even to tell my girlfriend her jeans look good when they're too tight. It may make her feel good about herself, but it's a lie to tell her something I don't really think.
You are tapping into a huge and fascinating philosophical debate that has raged throughout all of recorded history. Is there Good and Evil, or only what's good for me/you/us/them right now? Was the murderous sneak attack on Pearl Harbor "good" because it pushed the US into a war where they fought "evil" in the form of tyranny, murder, and oppression? Do you judge something by its intent, results, or some kind of universal natural rule that is supposed to be recognized by all mankind?
Another good example is the "family unit" in the USSR. The family was first purged and disbanded by law as a form of private ownership; marriages were called private prostitution and not desired nor acknowledged by the official government. They were "evil", a remnant of humanity's past ignorance and a violation of Communist doctrine. Then, when it was found that there was a natural order to the human family, and that mankind lived and functioned better that way, it was immediately relabeled as "good", desirable, ideal. There was no standard, only "what is good for the motherland right now in our eyes".
Fascinating, isn't it? I've got a very solid and grounded opinion on it, but that is enough of a derail I think