It's a fairly obvious thing to say, but no one is ever 100% in the right, any more than anyone else is every 100% in the wrong. It's a fairly obvious thing to say - but, like many obvious things, one which most people try to ignore. In arguments, as in wars, there has never been a moment in human relationships where right has been 100% with one side. Often, individual sides manage to undermine their own legitimacy or "high ground" without any input from the other side at all. (I wonder what I'm thinking of at the moment in global politics? - answers on a postcard, addressed to Guantanamo Bay ...).
It's in most people's interests - and particularly governments' - to ignore this uncomfortable ambiguity in human relations. Most nationalisms are founded on the culpability of "the other side": Greek and Turkish nationalisms, for example, couldn't survive in their current forms without their beliefs in the absolute guilt of the other side. And closer to home, there are even more obvious examples. Similarly, most playground arguments are based on "It was his fault," "No, it was his fault," "No, he started it," "No, he started it," "He did this to me," "But he did this first," "But he did this before that," and so on and so forth. In playground microcosm, we have the history of nationalisms.
One of the jobs of the writer, I think, is to recover the ambiguity behind human relations, and show that arguments are always more complicated than 100% right vs. 100% wrong. Novels in which feature a good side versus an evil side are rare, and generally not very good. And that includes the Bible, where right and wrong are often very ambivalent (cf. King David). Writers have to be alive to moral dubiousness, to everyday compromises, to moral ambiguity, to the sheer complexity of one person relating to one other person (let alone relations on a larger scale). On a moment to moment basis, relationships change in minor and major ways. Relationships are never simple, always infinitely complex mixtures of emotions, histories, conversations, interactions, body languages, power, politics, and so on. In our society, it's in very few people's interests to recognise this - but the job of the writer is to remind everyone that this is the case.