I'm writing an essay on relativism in LOTR

[Lightice]

Well really, what I'm going to get at especially is the question: "Do absolute, pure good and evil actually exist in LOTR?"

And I'm going to try to justify the answer "no". However, I need to be fully aware of both sides of the issue to argue anything in the first place.

Very true. Morgoth first wanted simply became different than his brothers and sisters while travelling in Darkness searching for Light, but as he never found it, he became bitter, and in the end corrupt. Corruption started from him, but he wasn't the corruption. And corruption is different from evil. Morgoth and those who followed him fell in corruption and darkness and in the end destruction. I however wouldn't call that "evil". As for the "good" guys, Eru wanted to keep in control of everything. It was rather like "Big Brother is watching" kind of thing, really. I wouldn't thus say, that Eru was 100% good, nor were Valar.
So nothing was pure. Only shades of gray.