The Line by Aleksandr Solzhenitsyn [KEYED AF ALERT]

Very true observation of our changes, but rather than our being 'sometimes justifying evil' but being both 'good and evil,' it is more accurate to see good as the things we've learned to like, and evil as the things we've learned to dislike. This avoids the problem of never knowing if you're 'justifying evil' or know the 'true good.' It also explains the pattern in the line's shifts- people whose interests align with yours shift towards 'good,' and when your own interests change, your past actions seem 'evil.' The author is on the right path, but needs to shed this constraining belief, or he will be badly off for it.