The way I choose to see it, in a truly objective world;
It's basically a black and white situation. Evil and Good are clear, distinct. They aren't philosophies, not really. They are sides, armies, forces.

In an objective world, the evil-thinking but neutral acting man is neutral, simply because he hasn't actively helped either side by deed. The forces of 'Good' and Evil' have neither prospered or lost in their esoteric war, in his case, so he remains on the sidelines until the day when he sees the perfect opportunity to 'indulge'. After that, he could be said to be Evil, in as much as he had physically sided with the Forces of Evil, in effect.

All of this and more is why I kind of dislike the concept of DnD having Objective, Cosmic Morality. It's just weird, and really un-intuitive to me.