Interesting point, actually- Sin is turning your back on God, not nessicarally the same as the moral negativity that we call 'evil'. You could, I suppose, be a Sinner whilst living a perfectly spiritual and morally correct life, becuase you are a strict athiest.

And if we really want to get nit-picky, we could also say that God did not create Sin at all; Sin is a word we use for estrangement from god, and therefore exists just because God exists in the mind of humans.