[Lord of Angmar]

I am of the opinion that evil in Ea is a fundamental and inherent part of the world

I agree, but while it may be a fundamental part in the world that does not mean that it is an inherently dominant character trait in an entire race. Many humans sin (according to the Catholic definition of the word), in fact most if not all humans have sinned in our lives, but this does not make us evil as a race. What I am saying is that evil can be part of a race and yet individuals of that race can still be defined by traits other than evil.

He will see that nothing exists or can be created that hath not its uttermost source in me.

This seems to prove his point. Since Tolkien described Illuvatar the Creator as the only one who could attain true perfection, then anything rooted in his creation cannot be utterly and inherently evil.