Long story short. Pixy was being indoctrinated by another fellow Ace Pilot who had joined a terror organization called AWWNB. As the battles continued to rage on Pixy saw the side he was fighting for, make morally reprehensible combat decisions in battle. Then he saw what Belka was willing do to their own soil and made up his mind he wasn't going to be fight for any particular side any more, since both sides had lots of blood on their hands. He joined AWWNB, it wasn't about betraying Cypher. It was about not being able to continue fighting on the wrong side of your own moral code.