It started small. It always does.
Nobody ever goes straight into eternal fiery pits of hell from a pure standing start. You gotta start off with a subtle coating of impurity, convince someone that a little immorality is fine, then you ramp up from there.
And, not to be too immodest, but I was one of the best. I'm the demon who got Joan of Arc right before she burned, after all.
But in all my time adding impurity to souls, I never thought about that taunting the angels and then talking to them might be removing my own impurity...