Even if you don't think the change is important, you should still be able to tell that skin color is more than a cosmetic, superficial qualitiy. Unlike clothing, makeup, and even eye color, skin color cannot be altered on a whim in the real world. You're essentially changing who the person is when you alter their race... this should be obvious.
You are who you want to be.
How others perceive you doesn't change who you are or what you are. Only you get to decide that.
Using the almost limitless freedom of mods to alter things that cannot be changed in real life does not remove the implications of such changes. If you swap out Fenris's body model with a human's, is he still an elf? No, even if you don't alter the coding and the game still treats him as such. It's the same principle..
And I completely disagree. If Fenris thinks he's an elf, then he's an elf. Who am I to challenge his identity?
If I take away your male body and give you a female body, does that stop you from being male? Of course not. You'd no longer be a cisgendered male, but you could still be male. And you would be the only person who got to decide that.