I don't think Suzaku's a traitor. He's just following what he believes is right. But just doing it the wrong way around. He's taking out all his anger on Lelouch. While that's NOT COOL, he doesn't see it like that. He believes Lelouch is what is making him act in a certain way (like using his geass) and he's fighting his true nature by denying the person who is the most like him.